Author: "Van Bemmel, Ilse" - Searchworks@Jio Institute Digital Library Search Results

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228 results on '"Van Bemmel, Ilse"'

1. The putative center in NGC 1052

Author: Baczko, Anne-Kathrin, Kadler, Matthias, Ros, Eduardo, Fromm, Christian M., Wielgus, Maciek, Perucho, Manel, Krichbaum, Thomas P., Baloković, Mislav, Blackburn, Lindy, Chan, Chi-kwan, Issaoun, Sara, Janssen, Michael, Ricci, Luca, Akiyama, Kazunori, Albentosa-Ruíz, Ezequiel, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Ball, David, Bandyopadhyay, Bidisha, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Dihingia, Indu K., Doeleman, Sheperd S., Dougall, Sean Taylor, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Edward, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Impellizzeri, C. M. Violette, Inoue, Makoto, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Kramer, Carsten, Kramer, Joana A., Kramer, Michael, Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lowitz, Amy E., Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Mulaudzi, Wanga, Müller, Cornelia, Müller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nair, Dhanya G., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Sánchez, Héctor Raúl Olivares, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Principe, Giacomo, Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Salas, León David Sosapanta, Souccar, Kamal, Stanway, Joshua S., Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Washington, Jasmin E., Weintroub, Jonathan, Wharton, Robert, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, and Zhao, Guang-Yao
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: Many active galaxies harbor powerful relativistic jets, however, the detailed mechanisms of their formation and acceleration remain poorly understood. To investigate the area of jet acceleration and collimation with the highest available angular resolution, we study the innermost region of the bipolar jet in the nearby low-ionization nuclear emission-line region (LINER) galaxy NGC 1052. We combined observations of NGC 1052 taken with VLBA, GMVA, and EHT over one week in the spring of 2017. For the first time, NGC 1052 was detected with the EHT, providing a size of the central region in-between both jet bases of 250 RS (Schwarzschild radii) perpendicular to the jet axes. This size estimate supports previous studies of the jets expansion profile which suggest two breaks of the profile at around 300 RS and 10000 RS distances to the core. Furthermore, we estimated the magnetic field to be 1.25 Gauss at a distance of 22 {\mu}as from the central engine by fitting a synchrotron-self absorption spectrum to the innermost emission feature, which shows a spectral turn-over at about 130 GHz. Assuming a purely poloidal magnetic field, this implies an upper limit on the magnetic field strength at the event horizon of 26000 Gauss, which is consistent with previous measurements. The complex, low-brightness, double-sided jet structure in NGC 1052 makes it a challenge to detect the source at millimeter (mm) wavelengths. However, our first EHT observations have demonstrated that detection is possible up to at least 230 GHz. This study offers a glimpse through the dense surrounding torus and into the innermost central region, where the jets are formed. This has enabled us to finally resolve this region and provide improved constraints on its expansion and magnetic field strength., Comment: 22 pages, 10 figures, published in A&A
Published: 2025
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2. A multi-frequency study of sub-parsec jets with the Event Horizon Telescope

Author: Röder, Jan, Wielgus, Maciek, Lobanov, Andrei P., Krichbaum, Thomas P., Nair, Dhanya G., Lee, Sang-Sung, Ros, Eduardo, Fish, Vincent L., Blackburn, Lindy, Chan, Chi-kwan, Issaoun, Sara, Janssen, Michael, Johnson, Michael D., Doeleman, Sheperd S., Bower, Geoffrey C., Crew, Geoffrey B., Tilanus, Remo P. J., Savolainen, Tuomas, Impellizzeri, C. M. Violette, Alberdi, Antxon, Baczko, Anne-Kathrin, Gómez, José L., Lu, Ru-Sen, Paraschos, Georgios F., Traianou, Efthalia, Goddi, Ciriaco, Kim, Daewon, Lisakov, Mikhail, Kovalev, Yuri Y., Voitsik, Petr A., Sokolovsky, Kirill V., Akiyama, Kazunori, Albentosa-Ruíz, Ezequiel, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Ball, David, Baloković, Mislav, Bandyopadhyay, Bidisha, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Bouman, Katherine L., Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Cruz-Osorio, Alejandro, Cui, Yuzhu, Curd, Brandon, Dahale, Rohan, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Dihingia, Indu K., Dougall, Sean Taylor, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fomalont, Edward, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gómez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Kramer, Carsten, Kramer, Joana A., Kramer, Michael, Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Loinard, Laurent, Lonsdale, Colin J., Lowitz, Amy E., MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Mulaudzi, Wanga, Müller, Cornelia, Müller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Sánchez, Héctor R. Olivares, Ortiz-León, Gisela N., Oyama, Tomoaki, özel, Feryal, Palumbo, Daniel C. M., Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Principe, Giacomo, Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Salas, León David Sosapanta, Souccar, Kamal, Stanway, Joshua S., Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Titus, Michael, Torne, Pablo, Toscano, Teresa, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib J., van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Washington, Jasmin E., Weintroub, Jonathan, Wharton, Robert, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The 2017 observing campaign of the Event Horizon Telescope (EHT) delivered the first very long baseline interferometry (VLBI) images at the observing frequency of 230 GHz, leading to a number of unique studies on black holes and relativistic jets from active galactic nuclei (AGN). In total, eighteen sources were observed: the main science targets, Sgr A* and M87 along with various calibrators. We investigated the morphology of the sixteen AGN in the EHT 2017 data set, focusing on the properties of the VLBI cores: size, flux density, and brightness temperature. We studied their dependence on the observing frequency in order to compare it with the Blandford-K\"onigl (BK) jet model. We modeled the source structure of seven AGN in the EHT 2017 data set using linearly polarized circular Gaussian components and collected results for the other nine AGN from dedicated EHT publications, complemented by lower frequency data in the 2-86 GHz range. Then, we studied the dependences of the VLBI core flux density, size, and brightness temperature on the frequency measured in the AGN host frame. We compared the observations with the BK jet model and estimated the magnetic field strength dependence on the distance from the central black hole. Our results indicate a deviation from the standard BK model, particularly in the decrease of the brightness temperature with the observing frequency. Either bulk acceleration of the jet material, energy transfer from the magnetic field to the particles, or both are required to explain the observations.
Published: 2025

3. First Very Long Baseline Interferometry Detections at 870{\mu}m

Author: Raymond, Alexander W., Doeleman, Sheperd S., Asada, Keiichi, Blackburn, Lindy, Bower, Geoffrey C., Bremer, Michael, Broguiere, Dominique, Chen, Ming-Tang, Crew, Geoffrey B., Dornbusch, Sven, Fish, Vincent L., García, Roberto, Gentaz, Olivier, Goddi, Ciriaco, Han, Chih-Chiang, Hecht, Michael H., Huang, Yau-De, Janssen, Michael, Keating, Garrett K., Koay, Jun Yi, Krichbaum, Thomas P., Lo, Wen-Ping, Matsushita, Satoki, Matthews, Lynn D., Moran, James M., Norton, Timothy J., Patel, Nimesh, Pesce, Dominic W., Ramakrishnan, Venkatessh, Rottmann, Helge, Roy, Alan L., Sánchez, Salvador, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Wagner, Jan, Weintroub, Jonathan, Wielgus, Maciek, Young, André, Akiyama, Kazunori, Albentosa-Ruíz, Ezequiel, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Bandyopadhyay, Bidisha, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Bouman, Katherine L., Boyce, Hope, Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Bronzwaer, Thomas, Bustamante, Sandra, Carlstrom, John E., Chael, Andrew, Chan, Chi-kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Crawford, Thomas M., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Dihingia, Indu K., Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fomalont, Edward, Fontana, Anne-Laure, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., Georgiev, Boris, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jones, Adam C., Joshi, Abhishek V., Jung, Taehyun, Karuppusamy, Ramesh, Kawashima, Tomohisa, Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Kocherlakota, Prashant, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Joana A., Kramer, Michael, Kubo, Derek, Kuo, Cheng-Yu, La Bella, Noemi, Lee, Sang-Sung, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lowitz, Amy E., Lu, Ru-Sen, MacDonald, Nicholas R., Mahieu, Sylvain, Maier, Doris, Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Montgomery, Joshua, Moriyama, Kotaro, Moscibrodzka, Monika, Mulaudzi, Wanga, Müller, Cornelia, Müller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Ni, Chunchong, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Sánchez, Héctor Raúl Olivares, Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Pen, Ue-Li, Piétu, Vincent, PopStefanija, Aleksandar, Porth, Oliver, Prather, Ben, Principe, Giacomo, Psaltis, Dimitrios, Pu, Hung-Yi, Raffin, Philippe A., Rao, Ramprasad, Rawlings, Mark G., Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Romero-Cañizales, Cristina, Ros, Eduardo, Roshanineshat, Arash, Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Salas, León David Sosapanta, Souccar, Kamal, Srinivasan, Ranjani, Stanway, Joshua S., Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Toma, Kenji, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Ward-Thompson, Derek, Wardle, John, Washington, Jasmin E., Wharton, Robert, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The first very long baseline interferometry (VLBI) detections at 870$\mu$m wavelength (345$\,$GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from the surface of the Earth, and the highest-frequency example of the VLBI technique to date. These include strong detections for multiple sources observed on inter-continental baselines between telescopes in Chile, Hawaii, and Spain, obtained during observations in October 2018. The longest-baseline detections approach 11$\,$G$\lambda$ corresponding to an angular resolution, or fringe spacing, of 19$\mu$as. The Allan deviation of the visibility phase at 870$\mu$m is comparable to that at 1.3$\,$mm on the relevant integration time scales between 2 and 100$\,$s. The detections confirm that the sensitivity and signal chain stability of stations in the Event Horizon Telescope (EHT) array are suitable for VLBI observations at 870$\mu$m. Operation at this short wavelength, combined with anticipated enhancements of the EHT, will lead to a unique high angular resolution instrument for black hole studies, capable of resolving the event horizons of supermassive black holes in both space and time., Comment: Corresponding author: S. Doeleman
Published: 2024
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4. A search for pulsars around Sgr A* in the first Event Horizon Telescope dataset

Author: Torne, Pablo, Liu, Kuo, Eatough, Ralph P., Wongphechauxsorn, Jompoj, Cordes, James M., Desvignes, Gregory, De Laurentis, Mariafelicia, Kramer, Michael, Ransom, Scott M., Chatterjee, Shami, Wharton, Robert, Karuppusamy, Ramesh, Blackburn, Lindy, Janssen, Michael, Chan, Chi-kwan, Crew, Geoffrey B., Matthews, Lynn D., Goddi, Ciriaco, Rottmann, Helge, Wagner, Jan, Sanchez, Salvador, Ruiz, Ignacio, Abbate, Federico, Bower, Geoffrey C., Salamanca, Juan J., Gomez-Ruiz, Arturo I., Herrera-Aguilar, Alfredo, Jiang, Wu, Lu, Ru-Sen, Pen, Ue-Li, Raymond, Alexander W., Shao, Lijing, Shen, Zhiqiang, Paubert, Gabriel, Sanchez-Portal, Miguel, Kramer, Carsten, Castillo, Manuel, Navarro, Santiago, John, David, Schuster, Karl-Friedrich, Johnson, Michael D., Rygl, Kazi L. J., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Bauboeck, Michi, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Bouman, Katherine L., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chang, Dominic O., Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Crawford, Thomas M., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, Deane, Roger, Dempsey, Jessica, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., Garcia, Roberto, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gomez, Jose L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Jeter, Britton, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Muller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Roy, Alan L., Ruszczyk, Chet, Sanchez-Arguelles, David, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, Andre, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Event Horizon Telescope (EHT) observed in 2017 the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz ($\lambda$=1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT datasets. The high observing frequency means that pulsars - which typically exhibit steep emission spectra - are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic Center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most-sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the Fast-Folding-Algorithm and single pulse search targeting both pulsars and burst-like transient emission; using the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction ($\lesssim$2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region., Comment: 33 pages, 7 figures, 6 Tables. Accepted for publication in ApJ
Published: 2023

5. Comparison of Polarized Radiative Transfer Codes used by the EHT Collaboration

Author: Prather, Ben S., Dexter, Jason, Moscibrodzka, Monika, Pu, Hung-Yi, Bronzwaer, Thomas, Davelaar, Jordy, Younsi, Ziri, Gammie, Charles F., Gold, Roman, Wong, George N., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chan, Chi-kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Müller, Cornelia, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Preciado-López, Jorge A., Psaltis, Dimitrios, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wu, Qingwen, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Interpretation of resolved polarized images of black holes by the Event Horizon Telescope (EHT) requires predictions of the polarized emission observable by an Earth-based instrument for a particular model of the black hole accretion system. Such predictions are generated by general relativistic radiative transfer (GRRT) codes, which integrate the equations of polarized radiative transfer in curved spacetime. A selection of ray-tracing GRRT codes used within the EHT collaboration is evaluated for accuracy and consistency in producing a selection of test images, demonstrating that the various methods and implementations of radiative transfer calculations are highly consistent. When imaging an analytic accretion model, we find that all codes produce images similar within a pixel-wise normalized mean squared error (NMSE) of 0.012 in the worst case. When imaging a snapshot from a cell-based magnetohydrodynamic simulation, we find all test images to be similar within NMSEs of 0.02, 0.04, 0.04, and 0.12 in Stokes I, Q, U , and V respectively. We additionally find the values of several image metrics relevant to published EHT results to be in agreement to much better precision than measurement uncertainties., Comment: Accepted for publication in ApJ
Published: 2023
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6. The Event Horizon Telescope Image of the Quasar NRAO 530

Author: Jorstad, Svetlana, Wielgus, Maciek, Lico, Rocco, Issaoun, Sara, Broderick, Avery E., Pesce, Dominic W., Liu, Jun, Zhao, Guang-Yao, Krichbaum, Thomas P., Blackburn, Lindy, Chan, Chi-Kwan, Janssen, Michael, Ramakrishnan, Venkatessh, Akiyama, Kazunori, Alberdi, Antxon, Algaba, Juan Carlos, Bouman, Katherine L., Cho, Ilje, Fuentes, Antonio, Gomez, Jose L., Gurwell, Mark, Johnson, Michael D., Kim, Jae-Young, Lu, Ru-Sen, Marti-Vidal, Ivan, Moscibrodzka, Monika, Poetzl, Felix M., Traianou, Efthalia, van Bemmel, Ilse, and Collaboration, the Event Horizon Telescope
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5-7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z=0.902 this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of $\sim$ 20 $\mu$as, both in total intensity and in linear polarization. We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of $\sim$5-8% and has a sub-structure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 $\mu$as along a position angle PA$\sim -$28$^\circ$. It includes two features with orthogonal directions of polarization (electric vector position angle, EVPA), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of linear polarization, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on ${\mu}$as scales, while simultaneous multi-wavelength monitoring will provide insight into the high energy emission origin.
Published: 2023
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7. CASA, the Common Astronomy Software Applications for Radio Astronomy

Author: THE CASA TEAM, Bean, Ben, Bhatnagar, Sanjay, Castro, Sandra, Meyer, Jennifer Donovan, Emonts, Bjorn, Garcia, Enrique, Garwood, Robert, Golap, Kumar, Villalba, Justo Gonzalez, Harris, Pamela, Hayashi, Yohei, Hoskins, Josh, Hsieh, Mingyu, Jagannathan, Preshanth, Kawasaki, Wataru, Keimpema, Aard, Kettenis, Mark, Lopez, Jorge, Marvil, Joshua, Masters, Joseph, McNichols, Andrew, Mehringer, David, Miel, Renaud, Moellenbrock, George, Montesino, Federico, Nakazato, Takeshi, Ott, Juergen, Petry, Dirk, Pokorny, Martin, Raba, Ryan, Rau, Urvashi, Schiebel, Darrell, Schweighart, Neal, Sekhar, Srikrishna, Shimada, Kazuhiko, Small, Des, Steeb, Jan-Willem, Sugimoto, Kanako, Suoranta, Ville, Tsutsumi, Takahiro, van Bemmel, Ilse M., Verkouter, Marjolein, Wells, Akeem, Xiong, Wei, Szomoru, Arpad, Griffith, Morgan, Glendenning, Brian, and Kern, Jeff
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: CASA, the Common Astronomy Software Applications, is the primary data processing software for the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), and is frequently used also for other radio telescopes. The CASA software can handle data from single-dish, aperture-synthesis, and Very Long Baseline Interferometery (VLBI) telescopes. One of its core functionalities is to support the calibration and imaging pipelines for ALMA, VLA, VLA Sky Survey (VLASS), and the Nobeyama 45m telescope. This paper presents a high-level overview of the basic structure of the CASA software, as well as procedures for calibrating and imaging astronomical radio data in CASA. CASA is being developed by an international consortium of scientists and software engineers based at the National Radio Astronomical Observatory (NRAO), the European Southern Observatory (ESO), the National Astronomical Observatory of Japan (NAOJ), and the Joint Institute for VLBI European Research Infrastructure Consortium (JIV-ERIC), under the guidance of NRAO., Comment: Accepted for publication in PASP (20 pages, 4 figures). Joint publication with CASA-VLBI paper
Published: 2022
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8. CASA on the fringe -- Development of VLBI processing capabilities for CASA

Author: van Bemmel, Ilse M., Kettenis, Mark, Small, Des, Janssen, Michael, Moellenbrock, George A., Petry, Dirk, Goddi, Ciriaco, Linford, Justin D., Rygl, Kazi L. J., Liuzzo, Elisabetta, Marcote, Benito, Bayandina, Olga S., Schweigart, Neal, Verkouter, Marjolein, Keimpema, Aard, Szomoru, Arpad, and van Langevelde, Huib Jan
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: New functionality to process Very Long Baseline Interferometry (VLBI) data has been implemented in the CASA package. This includes two new tasks to handle fringe fitting and VLBI-specific amplitude calibration steps. Existing tasks have been adjusted to handle VLBI visibility data and calibration meta-data properly. With these updates, it is now possible to process VLBI continuum and spectral line observations in CASA. This article describes the development and implementation, and presents an outline for the workflow when calibrating European VLBI Network or Very Long Baseline Array data in CASA. Though the CASA VLBI functionality has already been vetted extensively as part of the Event Horizon Telescope data processing, in this paper we compare results for the same dataset processed in CASA and AIPS. We find identical results for the two packages and conclude that CASA in some cases performs better, though it cannot match AIPS for single-core processing time. The new functionality in CASA allows for easy development of pipelines or Jupyter notebooks, and thus contributes to raising VLBI data processing to present day standards for accessibility, reproducibility, and reusability., Comment: PASP in press, joint submission with the CASA reference paper; 12 pages, 5 figures
Published: 2022
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9. The science case and challenges of space-borne sub-millimeter interferometry

Author: Gurvits, Leonid I., Paragi, Zsolt, Amils, Ricardo I., van Bemmel, Ilse, Boven, Paul, Casasola, Viviana, Conway, John, Davelaar, Jordy, Díez-González, M. Carmen, Falcke, Heino, Fender, Rob, Frey, Sándor, Fromm, Christian M., Gallego-Puyol, Juan D., García-Miró, Cristina, Garrett, Michael A., Giroletti, Marcello, Goddi, Ciriaco, Gómez, José L., van der Gucht, Jeffrey, Guirado, José Carlos, Haiman, Zoltán, Helmich, Frank, Hudson, Ben, Humphreys, Elizabeth, Impellizzeri, Violette, Janssen, Michael, Johnson, Michael D., Kovalev, Yuri Y., Kramer, Michael, Lindqvist, Michael, Linz, Hendrik, Liuzzo, Elisabetta, Lobanov, Andrei P., López-Fernández, Isaac, Malo-Gómez, Inmaculada, Masania, Kunal, Mizuno, Yosuke, Plavin, Alexander V., Rajan, Raj T., Rezzolla, Luciano, Roelofs, Freek, Ros, Eduardo, Rygl, Kazi L. J., Savolainen, Tuomas, Schuster, Karl, Venturi, Tiziana, Verkouter, Marjolein, de Vicente, Pablo, Visser, Pieter N. A. M., Wiedner, Martina C., Wielgus, Maciek, Wiik, Kaj, and Zensus, J. Anton
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10-20 microrcseconds. Further developments toward at least an order of magnitude "sharper" values are dictated by the needs of astrophysical studies and can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics (THEZA), has been proposed in the framework of the ESA Call for White Papers for the Voayage 2050 long term plan in 2019. In the current paper we discuss several approaches for addressing technological challenges of the THEZA concept. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes, data handling and processing. The paper briefly discusses approaches to the interferometric baseline state vector determination and synchronisation and heterodyning system. In combination with the original ESA Voyage 2050 White Paper, the current work sharpens the case for the next generation microarcsceond-level imaging instruments and provides starting points for further in-depth technology trade-off studies., Comment: The paper on 29 pages contains 12 figures, accepted for publication in Acta Astronautica, based on the presentation at the 72nd IAC, Dubai, UAE, October 2021
Published: 2022
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10. MeqSilhouette v2: Spectrally-resolved polarimetric synthetic data generation for the Event Horizon Telescope

Author: Natarajan, Iniyan, Deane, Roger, Martí-Vidal, Iván, Roelofs, Freek, Janssen, Michael, Wielgus, Maciek, Blackburn, Lindy, Blecher, Tariq, Perkins, Simon, Smirnov, Oleg, Davelaar, Jordy, Moscibrodzka, Monika, Chael, Andrew, Bouman, Katherine L., Kim, Jae-Young, Bernardi, Gianni, van Bemmel, Ilse, Falcke, Heino, Özel, Feryal, and Psaltis, Dimitrios
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present MeqSilhouette v2.0 (MeqSv2), a fully polarimetric, time-and frequency-resolved synthetic data generation software for simulating millimetre (mm) wavelength very long baseline interferometry (VLBI) observations with heterogeneous arrays. Synthetic data are a critical component in understanding real observations, testing calibration and imaging algorithms, and predicting performance metrics of existing or proposed sites. MeqSv2 applies physics-based instrumental and atmospheric signal corruptions constrained by empirically-derived site and station parameters to the data. The new version is capable of applying instrumental polarization effects and various other spectrally-resolved effects using the Radio Interferometry Measurement Equation (RIME) formalism and produces synthetic data compatible with calibration pipelines designed to process real data. We demonstrate the various corruption capabilities of MeqSv2 using different arrays, with a focus on the effect of complex bandpass gains on closure quantities for the EHT at 230 GHz. We validate the frequency-dependent polarization leakage implementation by performing polarization self-calibration of synthetic EHT data using PolSolve. We also note the potential applications for cm-wavelength VLBI array analysis and design and future directions., Comment: accepted for publication in MNRAS
Published: 2022
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11. Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

Author: Janssen, Michael, Falcke, Heino, Kadler, Matthias, Ros, Eduardo, Wielgus, Maciek, Akiyama, Kazunori, Baloković, Mislav, Blackburn, Lindy, Bouman, Katherine L., Chael, Andrew, Chan, Chi-kwan, Chatterjee, Koushik, Davelaar, Jordy, Edwards, Philip G., Fromm, Christian M., Gómez, José L., Goddi, Ciriaco, Issaoun, Sara, Johnson, Michael D., Kim, Junhan, Koay, Jun Yi, Krichbaum, Thomas P., Liu, Jun, Liuzzo, Elisabetta, Markoff, Sera, Markowitz, Alex, Marrone, Daniel P., Mizuno, Yosuke, Müller, Cornelia, Ni, Chunchong, Pesce, Dominic W., Ramakrishnan, Venkatessh, Roelofs, Freek, Rygl, Kazi L. J., van Bemmel, Ilse, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Barrett, John, Benson, Bradford A., Bintley, Dan, Blundell, Raymond, Boland, Wilfred, Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Chesler, Paul M., Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph P., Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gelles, Zachary, Gentaz, Olivier, Georgiev, Boris, Gold, Roman, Gómez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Himwich, Elizabeth, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kino, Motoki, Kofuji, Yutaro, Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Kuo, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Musoke, Gibwa, Mejías, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Rogers, Alan, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Sánchez, Salvador, Sánchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimeter wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to $10-100$ gravitational radii ($r_g=GM/c^2$) scales in nearby sources. Centaurus A is the closest radio-loud source to Earth. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our galactic center. A large southern declination of $-43^{\circ}$ has however prevented VLBI imaging of Centaurus A below ${\lambda}1$cm thus far. Here, we show the millimeter VLBI image of the source, which we obtained with the Event Horizon Telescope at $228$GHz. Compared to previous observations, we image Centaurus A's jet at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly-collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that Centaurus A's source structure resembles the jet in Messier 87 on ${\sim}500r_g$ scales remarkably well. Furthermore, we identify the location of Centaurus A's SMBH with respect to its resolved jet core at ${\lambda}1.3$mm and conclude that the source's event horizon shadow should be visible at THz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses., Comment: 27 pages, 9 figures. This is a post-peer-review, pre-copyedit version of an article published in Nature Astronomy. The final authenticated version is available online at: https://doi.org/10.1038/s41550-021-01417-w
Published: 2021
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12. The Variability of the Black-Hole Image in M87 at the Dynamical Time Scale

Author: Satapathy, Kaushik, Psaltis, Dimitrios, Ozel, Feryal, Medeiros, Lia, Dougall, Sean T., Chan, Chi-kwan, Wielgus, Maciek, Prather, Ben S., Wong, George N., Gammie, Charles F., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David R., Baloković, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope A., Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamente, Sandra, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas, Crew, Geoffrey B., Osorio, Alejandro Cruz, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica T., Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph, Falcke, Heino, Farah, Joseph R., Fish, Vincent, Fomalont, Edward B., Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez-Ruiz, Arturo I., Gómez, Jose L., Gu, Minfeng, Gurwell, Mark A., Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael, Hesper, Ronald, Ho, Luis C., Ho, Paul T., Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Rosales, Alejandra Jimenez, Johnson, Michael D., Jorstad, Svetlana G., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Miss Elisabetta, Lo, Wen-Ping, Lobanov, Andrei, Loinard, Laurent, Lonsdale, Colin J., Lu, Rusen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel, Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Matthews, Lynn, Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James, Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Mejias, Alejandro M., Musoke, Gibwa, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C., Park, Jongho, Patel, Nimesh A., Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard L., PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix, Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark, Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan E. E., Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi, Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhi-Qiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo, Titus, Michael, Toma, Kenji, Torne, Pablo, Traianou, E., Trent, Tyler, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John F., Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wiik, Kaj, Wu, Qingwen, Yoon, DooSoo, Young, Andre, Young, Ken H., Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The black-hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable to the 6-day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure phase measurements on all six linearly independent non-trivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of $\sim3-5^\circ$. The only triangles that exhibit substantially higher variability ($\sim90-180^\circ$) are the ones with baselines that cross visibility amplitude minima on the $u-v$ plane, as expected from theoretical modeling. We used two sets of General Relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black-hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black-hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas., Comment: Accepted for Publication in ApJ
Published: 2021
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13. Constraints on black-hole charges with the 2017 EHT observations of M87*

Author: Kocherlakota, Prashant, Rezzolla, Luciano, Falcke, Heino, Fromm, Christian M., Kramer, Michael, Mizuno, Yosuke, Nathanail, Antonios, Olivares, Hector, Younsi, Ziri, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chan, Chi-kwan, Chatterjee, Shami, Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Chesler, Paul M., Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Doeleman, Sheperd S., Eatough, Ralph P., Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Fraga-Encinas, Raquel, Friberg, Per, Ford, H. Alyson, Fuentes, Antonio, Galison, Peter, Gammie, Charles F., Garcia, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez, Jose L., Gomez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Marti-Vidal, Ivan, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejias, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Neilsen, Joseph, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi L. J., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, Andre, Young, Ken, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, Zhao, Shan-Shan, and Collaboration, The EHT
Subjects: General Relativity and Quantum Cosmology
Abstract: Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes., Comment: 15 pages, 4 figures, published in PRD on May 19
Published: 2021
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14. The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole

Author: Narayan, Ramesh, Palumbo, Daniel C. M., Johnson, Michael D., Gelles, Zachary, Himwich, Elizabeth, Chang, Dominic O., Ricarte, Angelo, Dexter, Jason, Gammie, Charles F., Chael, Andrew A., Collaboration, The Event Horizon Telescope, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Balokovic, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chan, Chi-kwan, Chatterjee, Shami, Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Chesler, Paul M., Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, DeLaurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Doeleman, Sheperd S., Eatough, Ralph P., Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Garcıa, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gomez, Jose L., Gomez-Ruiz, Arturo I., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Pin, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Martı-Vidal, Alan P. Marscher Ivan, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejıas, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Hector, Ortiz-Leon, Gisela N., Oyama, Tomoaki, Ozel, Feryal, Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Potzl, Felix M., Prather, Ben, Preciado-Lopez, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi L. J., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, Andre, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field in the emitting region, relativistic motion of the gas, strong gravitational lensing by the black hole, and parallel transport in the curved spacetime. We explore these effects using a simple model of an axisymmetric, equatorial accretion disk around a Schwarzschild black hole. By using an approximate expression for the null geodesics derived by Beloborodov (2002) and conservation of the Walker-Penrose constant, we provide analytic estimates for the image polarization. We test this model using currently favored general relativistic magnetohydrodynamic simulations of M87*, using ring parameters given by the simulations. For a subset of these with modest Faraday effects, we show that the ring model broadly reproduces the polarimetric image morphology. Our model also predicts the polarization evolution for compact flaring regions, such as those observed from Sgr A* with GRAVITY. With suitably chosen parameters, our simple model can reproduce the EVPA pattern and relative polarized intensity in Event Horizon Telescope images of M87*. Under the physically motivated assumption that the magnetic field trails the fluid velocity, this comparison is consistent with the clockwise rotation inferred from total intensity images., Comment: 29 pages, 11 figures, published in ApJ on May 3
Published: 2021
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15. A compact core-jet structure in the changing-look Seyfert NGC 2617

Author: Yang, Jun, Paragi, Zsolt, Beswick, Robert J., Chen, Wen, van Bemmel, Ilse M., Wu, Qingwen, An, Tao, Wu, Xiaocong, Fan, Lulu, Oonk, J. B. R., Liu, Xiang, and Wang, Weihua
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The nearby face-on spiral galaxy NGC 2617 underwent an unambiguous 'inside-out' multi-wavelength outburst in Spring 2013, and a dramatic Seyfert type change probably between 2010 and 2012, with the emergence of broad optical emission lines. To search for the jet activity associated with this variable accretion activity, we carried out multi-resolution and multi-wavelength radio observations. Using the very long baseline interferometric (VLBI) observations with the European VLBI Network (EVN) at 1.7 and 5.0 GHz, we find that NGC 2617 shows a partially synchrotron self-absorbed compact radio core with a significant core shift, and an optically thin steep-spectrum jet extending towards the north up to about two parsecs in projection. We also observed NGC 2617 with the electronic Multi-Element Remotely Linked Interferometer Network (e-MERLIN) at 1.5 and 5.5 GHz, and revisited the archival data of the Very Large Array (VLA) and the Very Long Baseline Array (VLBA). The radio core had a stable flux density of about 1.4 mJy at 5.0 GHz between 2013 June and 2014 January, in agreement with the expectation of a supermassive black hole in the low accretion rate state. The northern jet component is unlikely to be associated with the 'inside-out' outburst of 2013. Moreover, we report that most optically selected changing-look AGN at z<0.83 are sub-mJy radio sources in the existing VLA surveys at 1.4 GHz, and it is unlikely that they are more active than normal AGN at radio frequencies., Comment: 10 pages, 7 figures, accepted for publication in MNRAS
Published: 2021
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16. Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole

Author: Psaltis, Dimitrios, Medeiros, Lia, Christian, Pierre, Ozel, Feryal, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Asada, Keiichi, Azulay, Rebecca, Ball, David, Balokovic, Mislav, Barrett, John, Bintley, Dan, Blackburn, Lindy, Boland, Wilfred, Bower, Geoffrey C., Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chan, Chi-kwan, Chatterjee, Shami, Chatterjee, Koushik, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Conway, John E., Cordes, James M., Crew, Geoffrey B., Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Eatough, Ralph P., Falcke, Heino, Fish, Vincent L., Fomalont, Ed, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Gammie, Charles F., García, Roberto, Gentaz, Olivier, Goddi, Ciriaco, Gomez, Jose L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Jae-Young, Kim, Junhan, Kim, Jongsoo, Kino, Motoki, Koay, Jun Yi, Koch, Patrick M., Koyama, Shoko, Kramer, Michael, Kramer, Carsten, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Lonsdale, Colin, Lu, Ru-Sen, Mao, Jirong, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Ivan, Matsushita, Satoki, Mizuno, Yosuke, Mizuno, Izumi, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Muller, Cornelia, Musoke, Gibwa, Mejías, Alejandro Mus, Nagai, Hiroshi, Nagar, Neil M., Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Neri, Roberto, Noutsos, Aristeidis, Okino, Hiroki, Olivares, Hector, Oyama, Tomoaki, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pietu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Prather, Ben, Preciado-Lopez, Jorge A., Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Ryan, Benjamin R., Rygl, Kazi L. J., Sanchez, Salvador, Sanchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Tazaki, Fumie, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Trent, Tyler, Traianou, Efthalia, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Wardle, John, Ward-Thompson, Derek, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wong, George N., Wu, Qingwen, Yoon, Doosoo, Young, Andre, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zhao, Shan-Shan, and Collaboration, the EHT
Subjects: General Relativity and Quantum Cosmology, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. We show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-Newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. The new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources., Comment: Physical Review Letters
Published: 2020
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17. VLBI20-30: a scientific roadmap for the next decade -- The future of the European VLBI Network

Author: Venturi, Tiziana, Paragi, Zsolt, Lindqvist, Michael, Bartkiewicz, Anna, Beswick, Rob, Bogdanović, Tamara, Brisken, Walter, Charlot, Patrick, Colomer, Francisco, Conway, John, Frey, Sándor, Guirado, José Carlos, Gurvits, Leonid, van Langevelde, Huib, Lobanov, Andrei, McKean, John, Morganti, Raffaella, Muxlow, Tom, Pérez-Torres, Miguel, Rygl, Kazi, Schulz, Robert, Szomoru, Arpad, de Vicente, Pablo, An, Tao, Anglada, Guillem, Argo, Megan, Azulay, Rebecca, van Bemmel, Ilse, Bocanegra, Tatiana, Boccardi, Biagina, Castangia, Paola, Chibueze, James, Cimò, Giuseppe, Climent, Juan-Bautista, Deane, Roger, Deller, Adam, Dodson, Richard, Duev, Dmitry, Etoka, Sandra, Fenech, Danielle, Gabányi, Krisztina, Gabuzda, Denise, Garrett, Michael, Gawroński, Marcin, Ghirlanda, Giancarlo, Giroletti, Marcello, Goddi, Ciriaco, Gómez, Jose Luis, Gray, Malcolm, Greaves, Jane, Hessels, Jason, van der Horst, Alexander, Hunter, Todd, Laing, Robert, Lal, Dharam Vir, Lambert, Sébastien, Loinard, Laurent, Marcote, Benito, Merloni, Andrea, Miller-Jones, James, Calvés, Guifré Molera, Moscadelli, Luca, Olofsson, Hans, Petrov, Leonid, Pizzo, Roberto, Possenti, Andrea, Quiroga-Nuñez, Luis Henry, Reynolds, Cormac, Richards, Anita, Rioja, Maria, Sanna, Alberto, Savolainen, Tuomas, Sbarrato, Tullia, Spingola, Cristiana, Surcis, Gabriele, Trigilio, Corrado, Varenius, Eskil, Vlemmings, Wouter, van Velzen, Sjoert, and van der Walt, Johan
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: This white paper describes the science case for Very Long Baseline Interferometry (VLBI) and provides suggestions towards upgrade paths for the European VLBI Network (EVN). The EVN is a distributed long-baseline radio interferometric array, that operates at the very forefront of astronomical research. Recent results, together with the new science possibilities outlined in this vision document, demonstrate the EVN's potential to generate new and exciting results that will transform our view of the cosmos. Together with e-MERLIN, the EVN provides a range of baseline lengths that permit unique studies of faint radio sources to be made over a wide range of spatial scales. The science cases are reviewed in six chapters that cover the following broad areas: cosmology, galaxy formation and evolution, innermost regions of active galactic nuclei, explosive phenomena and transients, stars and stellar masers in the Milky Way, celestial reference frames and space applications. The document concludes with identifying the synergies with other radio, as well as multi-band/multi-messenger instruments, and provide the recommendations for future improvements. The appendices briefly describe other radio VLBI arrays, the technological framework for EVN developments, and a selection of spectral lines of astrophysical interest below 100 GHz. The document includes a glossary for non-specialists, and a list of acronyms at the end., Comment: Editors: Tiziana Venturi, Zsolt Paragi, Michael Lindqvist. "EVN Vision Document (2020)", 7 chapters, 3 appendices, 191 pages, 64 figures. Chapter coordinators and all the contributors are listed in the document
Published: 2020

18. A probabilistic approach to phase calibration: I. Effects of source structure on fringe-fitting

Author: Natarajan, Iniyan, Deane, Roger, van Bemmel, Ilse, van Langevelde, Huib Jan, Small, Des, Kettenis, Mark, Paragi, Zsolt, Smirnov, Oleg, and Szomoru, Arpad
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We propose a probabilistic framework for performing simultaneous estimation of source structure and fringe-fitting parameters in Very Long Baseline Interferometry (VLBI) observations. As a first step, we demonstrate this technique through the analysis of synthetic short-duration Event Horizon Telescope (EHT) observations of various geometric source models at 230 GHz, in the presence of baseline-dependent thermal noise. We perform Bayesian parameter estimation and model selection between the different source models to obtain reliable uncertainty estimates and correlations between various source and fringe-fitting related model parameters. We also compare the Bayesian posteriors with those obtained using widely-used VLBI data reduction packages such as CASA and AIPS, by fringe-fitting 200 Monte Carlo simulations of each source model with different noise realisations, to obtain distributions of the Maximum A Posteriori (MAP) estimates. We find that, in the presence of resolved asymmetric source structure and a given array geometry, the traditional practice of fringe-fitting with a point source model yields appreciable offsets in the estimated phase residuals, potentially biasing or limiting the dynamic range of the starting model used for self-calibration. Simultaneously estimating the source structure earlier in the calibration process with formal uncertainties improves the precision and accuracy of fringe-fitting and establishes the potential of the available data especially when there is little prior information. We also note the potential applications of this method to astrometry and geodesy for specific science cases and the planned improvements to the computational performance and analyses of more complex source distributions., Comment: accepted for publication in MNRAS
Published: 2020
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19. A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances

Author: Fallows, Richard A., Forte, Biagio, Astin, Ivan, Allbrook, Tom, Arnold, Alex, Wood, Alan, Dorrian, Gareth, Mevius, Maaijke, Rothkaehl, Hanna, Matyjasiak, Barbara, Krankowski, Andrzej, Anderson, James M., Asgekar, Ashish, Avruch, I. Max, Bentum, Mark, Bisi, Mario M., Butcher, Harvey R., Ciardi, Benedetta, Dabrowski, Bartosz, Damstra, Sieds, de Gasperin, Francesco, Duscha, Sven, Eislöffel, Jochen, Franzen, Thomas M. O., Garrett, Michael A., Grie\b{eta}meier, Jean-Matthias, Gunst, André W., Hoeft, Matthias, Hörandel, Jörg R., Iacobelli, Marco, Intema, Huib T., Koopmans, Leon V. E., Maat, Peter, Mann, Gottfried, Nelles, Anna, Paas, Harm, Pandey, Vishambhar N., Reich, Wolfgang, Rowlinson, Antonia, Ruiter, Mark, Schwarz, Dominik J., Serylak, Maciej, Shulevski, Aleksander, Smirnov, Oleg M., Soida, Marian, Steinmetz, Matthias, Thoudam, Satyendra, Toribio, M. Carmen, van Ardenne, Arnold, van Bemmel, Ilse M., van der Wiel, Matthijs H. D., van Haarlem, Michiel P., Vermeulen, René C., Vocks, Christian, Wijers, Ralph A. M. J., Wucknitz, Olaf, Zarka, Philippe, and Zucca, Pietro
Subjects: Astrophysics - Earth and Planetary Astrophysics, Physics - Geophysics, Physics - Space Physics
Abstract: This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cas A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10-80MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR "core" reveals two different velocities in the scintillation pattern: a primary velocity of ~30m/s with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110m/s with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller--scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported., Comment: 24 pages, 16 figures. Accepted for open-access publication in the Journal of Space Weather and Space Climate. For associated movie file, see https://www.swsc-journal.org/10.1051/swsc/2020010/olm
Published: 2020

20. First M87 Event Horizon Telescope Results and the Role of ALMA

Author: Goddi, Ciriaco, Crew, Geoff, Impellizzeri, Violette, Marti-Vidal, Ivan, Matthews, Lynn D., Messias, Hugo, Rottmann, Helge, Alef, Walter, Blackburn, Lindy, Bronzwaer, Thomas, Chan, Chi-Kwan, Davelaar, Jordy, Deane, Roger, Dexter, Jason, Doeleman, Shep, Falcke, Heino, Fish, Vincent L., Fraga-Encinas, Raquel, Fromm, Christian M., Herrero-Illana, Ruben, Issaoun, Sara, James, David, Janssen, Michael, Kramer, Michael, Krichbaum, Thomas P., De Laurentis, Mariafelicia, Liuzzo, Elisabetta, Mizuno, Yosuke, Moscibrodzka, Monika, Natarajan, Iniyan, Porth, Oliver, Rezzolla, Luciano, Rygl, Kazi, Roelofs, Freek, Ros, Eduardo, Roy, Alan L., Shao, Lijing, van Langevelde, Huib Jan, van Bemmel, Ilse, Tilanus, Remo, Torne, Pablo, Wielgus, Maciek, Younsi, Ziri, and Zensus, J. Anton
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: In April 2019, the Event Horizon Telescope (EHT) collaboration revealed the first image of the candidate super-massive black hole (SMBH) at the centre of the giant elliptical galaxy Messier 87 (M87). This event-horizon-scale image shows a ring of glowing plasma with a dark patch at the centre, which is interpreted as the shadow of the black hole. This breakthrough result, which represents a powerful confirmation of Einstein's theory of gravity, or general relativity, was made possible by assembling a global network of radio telescopes operating at millimetre wavelengths that for the first time included the Atacama Large Millimeter/ submillimeter Array (ALMA). The addition of ALMA as an anchor station has enabled a giant leap forward by increasing the sensitivity limits of the EHT by an order of magnitude, effectively turning it into an imaging array. The published image demonstrates that it is now possible to directly study the event horizon shadows of SMBHs via electromagnetic radiation, thereby transforming this elusive frontier from a mathematical concept into an astrophysical reality. The expansion of the array over the next few years will include new stations on different continents - and eventually satellites in space. This will provide progressively sharper and higher-fidelity images of SMBH candidates, and potentially even movies of the hot plasma orbiting around SMBHs. These improvements will shed light on the processes of black hole accretion and jet formation on event-horizon scales, thereby enabling more precise tests of general relativity in the truly strong field regime., Comment: 11 pages + cover page, 6 figures
Published: 2019
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21. CASA on the fringe: VLBI data processing in the CASA software package

Author: van Bemmel, Ilse, Small, Des, Kettenis, Mark, Szomoru, Arpad, Moellenbrock, George, and Janssen, Michael
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: In recent years new functionality for VLBI data processing has been added to the CASA package. This paper presents the new CASA tasks 'fringefit' and 'accor', which are closely matched to their AIPS counterparts FRING and ACCOR. Several CASA tasks received upgrades to handle VLBI specific metadata. With the current CASA release VLBI data processing is possible, and functionality will be expanded in the upcoming release. Longer term developments include fringe fitting of broad, non-continuous frequency bands and dispersive delays, which will ensure that the number of use cases for VLBI calibration will increase in future CASA releases., Comment: 5 pages, 2 figures, EVN 2018 symposium proceedings
Published: 2019

22. High sensitivity VLBI with SKA

Author: García-Miró, Cristina, Chrysostomou, Antonio, Paragi, Zsolt, and van Bemmel, Ilse
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Square Kilometre Array (SKA), with the aim of achieving a collecting area of one square kilometre, will be the world's largest radio telescope. A scientific collaboration between 12 countries (with more to join), it will consist of one Observatory with 2 telescopes located in South Africa and Australia. The telescope deployment is planned in two phases, but even in its first stage (SKA1) it will already enable transformational science in a broad range of scientific objectives. The inclusion of SKA1 in the Global VLBI networks (SKA-VLBI) will provide access to very high angular resolution to SKA science programmes in anticipation of the science to be realized with the full telescope deployment (SKA2). This contribution provides an overview of the SKA Observatory VLBI capability, the key operational concepts and outlines the need to update the science use cases., Comment: 11 pages, 6 figures, conference
Published: 2019

23. rPICARD: A CASA-based Calibration Pipeline for VLBI Data. Calibration and imaging of 7 mm VLBA observations of the AGN jet in M87

Author: Janssen, Michael, Goddi, Ciriaco, van Bemmel, Ilse M., Kettenis, Mark, Small, Des, Liuzzo, Elisabetta, Rygl, Kazi, Martí-Vidal, Ivan, Blackburn, Lindy, Wielgus, Maciek, and Falcke, Heino
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: (Abridged) The CASA software suite, can now reduce very long baseline interferometry (VLBI) data with the recent addition of a fringe fitter. Here, we present the Radboud PIpeline for the Calibration of high Angular Resolution Data (rPICARD), which is an open-source VLBI calibration and imaging pipeline built on top of the CASA framework. The pipeline is capable of reducing data from different VLBI arrays. It can be run non-interactively after only a few non-default input parameters are set and delivers high-quality calibrated data. CPU scalability based on a message-passing interface (MPI) implementation ensures that large bandwidth data from future arrays can be processed within reasonable computing times. Phase calibration is done with a Schwab-Cotton fringe fit algorithm. For the calibration of residual atmospheric effects, optimal solution intervals are determined based on the signal-to-noise ratio (S/N) of the data for each scan. Different solution intervals can be set for different antennas in the same scan to increase the number of detections in the low S/N regime. These novel techniques allow rPICARD to calibrate data from different arrays, including high-frequency and low-sensitivity arrays. The amplitude calibration is based on standard telescope metadata, and a robust algorithm can solve for atmospheric opacity attenuation in the high-frequency regime. Standard CASA tasks are used for CLEAN imaging and self-calibration. In this work we demonstrate the capabilities of rPICARD by calibrating and imaging 7 mm VLBA data of the central radio source in the M87 galaxy. The reconstructed jet image reveals a complex collimation profile and edge-brightened structure. A potential counter-jet is detected that has 10 % of the brightness of the approaching jet. This constrains jet speeds close to the radio core to about half the speed of light for small inclination angles., Comment: Accepted for publication Astronomy and Astrophysics. Code available at https://bitbucket.org/M_Janssen/picard
Published: 2019
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24. The Lockman Hole with LOFAR - Searching for GPS and CSS sources at low frequencies

Author: Mahony, Elizabeth K., Morganti, Raffaella, Prandoni, Isabella, and van Bemmel, Ilse
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: The Lockman Hole Project is a wide international collaboration aimed at exploiting the multi-band extensive and deep information available for the Lockman Hole region, with the aim of better characterizing the physical and evolutionary properties of the various source populations detected in deep radio fields. Recent observations with the LOw-Frequency ARray (LOFAR) extends the multi-frequency radio information currently available for the Lockman Hole (from 350 MHz up to 15 GHz) down to 150 MHz, allowing us to explore a new radio spectral window for the faint radio source population. These LOFAR observations allow us to study the population of sources with spectral peaks at lower radio frequencies, providing insight into the evolution of GPS and CSS sources. In this general framework, I present preliminary results from 150 MHz LOFAR observations of the Lockman Hole field., Comment: Proceedings of the "5th Workshop on Compact Steep Spectrum and GHz-peaked Spectrum Radio Sources". To be published in Astronomische Nachrichten (6 pages)
Published: 2015
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25. A new period of activity in the core of NGC660

Author: Argo, Megan, van Bemmel, Ilse, Connolly, Sam, and Beswick, Robert
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: The core of the nearby galaxy NGC660 has recently undergone a spectacular radio outburst; using a combination of archival radio and Chandra X-ray data, together with new observations, the nature of this event is investigated. Radio observations made using e-MERLIN in mid-2013 show a new compact and extremely bright continuum source at the centre of the galaxy. High angular resolution observations carried out with the European VLBI Network show an obvious jet-like feature to the north east and evidence of a weak extension to the west, possibly a counter-jet. We also examine high angular resolution HI spectra of these new sources, and the radio spectral energy distribution using the new wide-band capabilities of e-MERLIN. We compare the properties of the new object with possible explanations, concluding that we are seeing a period of new AGN activity in the core of this polar ring galaxy., Comment: 9 pages, 7 figures. Accepted for publication in MNRAS
Published: 2015
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26. A relation between circumnuclear HI, dust, and optical cores in low-power radio galaxies

Author: van Bemmel, Ilse M., Morganti, Raffaella, Oosterloo, Tom, and van Moorsel, Gustaaf
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: From new observations and literature data we investigate the presence of HI, dust, and optical cores in the central kiloparsec of low-power radio galaxies. The goal of this pilot study is to identify physical relations between these components, which can help us to study kinematics and feeding mechanisms in future samples of active galaxies. Our results are consistent with neutral gas being associated with dust on sub-kiloparsec scales. Objects that have HI absorption always have significant amounts of dust in their host galaxy. If there is no visible dust in the host galaxy, there is also no HI absorption. The presence of an unresolved optical core correlates with the HI column density, with the core being absent in high column density sources. This work opens a path for studying the kinematics of cold material in the central regions of active galaxies by combining information of HI absorption and molecular lines. Consistent with previous work, we find no evidence for a compact, parsec-scale obscuring torus in low-power radio galaxies., Comment: Accepted for publication in A&A
Published: 2012
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27. Mid-frequency aperture arrays: the future of radio astronomy

Author: van Bemmel, Ilse M., van Ardenne, Arnold, de Vaate, Jan Geralt bij, Faulkner, Andrew J., and Morganti, Raffaella
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Aperture array (AA) technology is at the forefront of new developments and discoveries in radio astronomy. Currently LOFAR is successfully demonstrating the capabilities of dense and sparse AA's at low frequencies. For the mid-frequencies, from 450 to 1450MHz, AA's still have to prove their scientific value with respect to the existing dish technology. Their large field-of-view and high flexibility puts them in an excellent position to do so. The Aperture Array Verification Program is dedicated to demonstrate the feasibility of AA's for science in general and SKA in particular. For the mid-frequency range this has lead to the development of EMBRACE, which has already demonstrated the enormous flexibility of AA systems by observing HI and a pulsar simultaneously. It also serves as a testbed to demonstrate the technological reliability and stability of AA's. The next step will put AA technology at a level where it can be used for cutting-edge science. In this paper we discuss the developments to move AA technology from an engineering activity to a fully science capable instrument. We present current results from EMBRACE, ongoing tests of the system, and plans for EMMA, the next step in mid-frequency AA technology., Comment: 8 pages, 7 figures, proceedings of Resolving The Sky - Radio Astronomy: Past, Present and Future (RTS2012), April 17-20, 2012, Manchester, UK
Published: 2012

28. LOFAR and APERTIF surveys of the radio sky: probing shocks and magnetic fields in galaxy clusters

Author: Rottgering, Huub, Afonso, Jose, Barthel, Peter, Batejat, Fabien, Best, Philip, Bonafede, Annalisa, Bruggen, Marcus, Brunetti, Gianfranco, Chyzy, Krzysztof, Conway, John, De Gasperin, Francesco, Ferrari, Chiara, Haverkorn, Marijke, Heald, George, Hoeft, Matthias, Jackson, Neal, Jarvis, Matt, Ker, Louise, Lehnert, Matt, Macario, Giulia, McKean, John, Miley, George, Morganti, Raffaella, Oosterloo, Tom, Orru, Emanuela, Pizzo, Roberto, Rafferty, David, Shulevski, Alexander, Tasse, Cyril, van Bemmel, Ilse, van der Tol, Bas, van Weeren, Reinout, Verheijen, Marc, White, Glenn, and Wise, Michael
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF phased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from \sim 15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fundamental issues related the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters., Comment: 11 pages, 2 figures, Invited talk at the conference "Diffuse Relativistic Plasmas", Bangalore, 1-4 March 2011; in press for publication in special issue of Journal of Astrophysics and Astronomy
Published: 2011
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29. LOFAR: Recent imaging results & future prospects

Author: Heald, George, Bell, Michael R., Horneffer, Andreas, Offringa, André R., Pizzo, Roberto, van der Tol, Sebastiaan, van Weeren, Reinout J., van Zwieten, Joris E., Anderson, James M., Beck, Rainer, van Bemmel, Ilse, Bîrzan, Laura, Bonafede, Annalisa, Conway, John, Ferrari, Chiara, De Gasperin, Francesco, Haverkorn, Marijke, Jackson, Neal, Macario, Giulia, McKean, John, Miraghaei, Halime, Orrù, Emanuela, Rafferty, David, Röttgering, Huub, Scaife, Anna, Shulevski, Aleksandar, Sotomayor, Carlos, Tasse, Cyril, Trasatti, Monica, and Wucknitz, Olaf
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Low Frequency Array (LOFAR) is under construction in the Netherlands and in several surrounding European countries. In this contribution, we describe the layout and design of the telescope, with a particular emphasis on the imaging characteristics of the array when used in its "standard imaging" mode. After briefly reviewing the calibration and imaging software used for LOFAR image processing, we show some recent results from the ongoing imaging commissioning efforts. We conclude by summarizing future prospects for the use of LOFAR in observing the little-explored low frequency Universe., Comment: Accepted for publication in special issue of Journal of Astrophysics and Astronomy: conference proceedings of "Diffuse Relativistic Plasmas" conference, Bangalore, 1-4 March 2011
Published: 2011
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30. LOFAR: Early imaging results from commissioning for Cygnus A

Author: McKean, John, Ker, Louise, van Weeren, Reinout J., Batejat, Fabien, Birzan, Laura, Bonafede, Annalisa, Conway, John, De Gasperin, Francesco, Ferrari, Chiara, Heald, George, Jackson, Neal, Macario, Giulia, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Rottgering, Huub, Shulevski, Aleksandar, Tasse, Cyril, van der Tol, Sebastiaan, van Bemmel, Ilse, van Diepen, Ger, and van Zwieten, Joris E.
Subjects: Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Low Frequency Array (LOFAR) will operate between 10 and 250 MHz, and will observe the low frequency Universe to an unprecedented sensitivity and angular resolution. The construction and commissioning of LOFAR is well underway, with over 27 of the Dutch stations and five International stations routinely performing both single-station and interferometric observations over the frequency range that LOFAR is anticipated to operate at. Here, we summarize the capabilities of LOFAR and report on some of the early commissioning imaging of Cygnus A., Comment: 6 pages, 4 figures. 10th European VLBI Network Symposium and EVN Users Meeting: VLBI and the new generation of radio arrays, Manchester, UK, September 20-24, 2010
Published: 2011

31. Polarization and kinematics in Cygnus A

Author: van Bemmel, Ilse M., Vernet, Joel, Fosbury, Robert A. E., and Lamers, Henny J. G. L. M.
Subjects: Astrophysics
Abstract: From optical spectropolarimetry of Cygnus A we conclude that the scattering medium in the ionization cones in Cygnus A is moving outward at a speed of 170+-34 km/s, and that the required momentum can be supplied by the radiation pressure of an average quasar. Such a process could produce a structure resembling the observed ionization cones, which are thought to result from shadowing by a circumnuclear dust torus. We detect a polarized red wing in the [O III] emission lines arising from the central kiloparsec of Cygnus A. This wing is consistent with line emission created close to the boundary of the broad-line region., Comment: 5 pages, accepted for publication in MNRAS letters
Published: 2003
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32. Far-Infrared/Millimetre Emission in 3C Ssources. Dust in Radio Galaxies and Quasars

Author: Andreani, Paola, Fosbury, Robert A. E., van Bemmel, Ilse, and Freudling, Wolfram
Subjects: Astrophysics
Abstract: We present far-infrared and millimetric observations of a sample of 3C objects. Millimetre data were taken at 1.25 mm with the IRAM 30m antenna feeding the MPIfR bolometer array. Mid-infrared (MIR) and far-infrared (FIR) photometry were carried out with the ISOCAM and ISOPHOT cameras on the ISO Satellite. Additional FIR IRAS observations are also included. We present the entire Spectral Energy Distributions (SEDs) from the UV to radio and discuss the emitting mechanisms. Two composite spectra, one for the radio galaxies and one for the radio quasars, are built in the object rest frame. While the SEDs of the two classes differ, they are indistinguishable in the MIR and FIR range where they probably arise as thermal emission from a dusty torus and a larger-scale (cooler) dust distribution in the host galaxy., Comment: 15 pages, A&A, in press
Published: 2001
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33. Broad-line radio galaxies: old and feeble?

Author: van Bemmel, Ilse and Barthel, Peter
Subjects: Astrophysics
Abstract: Far-infrared photometry of broad-line radio galaxies shows this class of AGN to consist of many hot and some cool infrared emitters, with peaks in their spectral energy distributions around 25 micron or longward of 60 micron, respectively. Quantitative analysis indicates that this distribution relates to a substantial dispersion in the strength of the cool dust component: broad-line radio galaxies are relatively poor in large-scale dust. Possibly they have undergone a different merger evolution, or are relatively old AGN., Comment: Accepted for publication in A&A Letters
Published: 2001
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34. The broad-line radio galaxy story

Author: van Bemmel, Ilse
Subjects: Astrophysics
Abstract: In this paper I discuss the issue of the so-called 25 micron-peakers, which were discovered with IRAS, and consist almost solely of broad-line radio galaxies. I find that this peak is caused by the absence of colder dust that emits at 60 micron and not by an excess of hot dust, as suggested by the name. On optical images, the 25 micron-peakers show a lack of extended dust. The peakers are consistent with being in a later evolutionary stage, in which all the extended dust has been formed into stars and the dust torus is smaller. If the 60 micron dust is heated by stars, there might be a correlation between the star-formation rate and the power of the AGN., Comment: 6 pages, 3 figures, contribution to the 'FIRSED2000' conference, eds Barthel, van Bemmel & Wilkes. Uses elsart.cls (included)
Published: 2001

35. Millimeter observations of radio-loud active galaxies

Author: van Bemmel, Ilse and Bertoldi, Frank
Subjects: Astrophysics
Abstract: In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal emission. An extrapolation of the non-thermal radio spectrum indicates that the contribution of synchrotron emission to the far-infrared is less than 10% in quasars, and negligible in the radio galaxies. The quasars in the sample show signs of relativistic beaming at millimeter wavelengths, and the quasar 3C334 shows evidence for strong variability., Comment: 6 pages, 1 figure, accepted by A&A
Published: 2001
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36. ISOPHOT observations of 3CR quasars and radio galaxies

Author: van Bemmel, Ilse M., Barthel, Peter D., and de Graauw, Thijs
Subjects: Astrophysics
Abstract: In order to check for consistency with the radio-loud AGN unification scheme, ISOPHOT data obtained for two small sets of intermediate redshift steep-spectrum 3CR radio galaxies and quasars are being examined. Supplementary submillimeter and centimeter radio data for the quasars are also taken into account, in order to assess the magnitude of any beamed nonthermal radiation. The fact that we find broad-lined objects to be somewhat more luminous in their far-infrared output than narrow-lined objects, hints at a contradiction to the unification scheme. However, as the sample objects are not particularly well matched, the sample size is small, and the FIR radiation may still be partly anisotropic, this evidence is, at the moment, weak., Comment: 10 pages, 2 figures, accepted for publication in Astronomy & Astrophysics
Published: 2000

37. Infrared emission from radio-loud active nuclei

Author: van Bemmel, Ilse M., Barthel, Peter D., and de Graauw, Thijs
Subjects: Astrophysics
Abstract: In order to test the unification scheme for double-lobed radio sources, the far-infrared properties of matched samples of radio-galaxies and radio-loud quasars were studied using ISOPHOT. The quasar data were complemented with nearly simultaneous submillimeter and centimeter radio data. The results show that quasars are generally brighter than radio-galaxies in their far-infrared output and that beamed non-thermal radiation must be excluded as source for this infrared excess. However, non-thermal flares or optically thick tori can still reconcile these results with the unification scheme., Comment: 4 pages including 1 figure, to be published in the proceedings of ESA conference 'The Universe as seen by ISO', ed. M. Kessler (ESA Special Publications series SP-427)
Published: 1999

38. A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set

Author: Torne, Pablo, primary, Liu, Kuo, additional, Eatough, Ralph P., additional, Wongphechauxsorn, Jompoj, additional, Cordes, James M., additional, Desvignes, Gregory, additional, De Laurentis, Mariafelicia, additional, Kramer, Michael, additional, Ransom, Scott M., additional, Chatterjee, Shami, additional, Wharton, Robert, additional, Karuppusamy, Ramesh, additional, Blackburn, Lindy, additional, Janssen, Michael, additional, Chan, Chi-kwan, additional, Crew, Geoffrey, B., additional, Matthews, Lynn D., additional, Goddi, Ciriaco, additional, Rottmann, Helge, additional, Wagner, Jan, additional, Sánchez, Salvador, additional, Ruiz, Ignacio, additional, Abbate, Federico, additional, Bower, Geoffrey C., additional, Salamanca, Juan J., additional, Gómez-Ruiz, Arturo I., additional, Herrera-Aguilar, Alfredo, additional, Jiang 江, Wu 悟, additional, Lu 路, Ru-Sen 如森, additional, Pen, Ue-Li, additional, Raymond, Alexander W., additional, Shao, Lijing, additional, Shen 沈, Zhiqiang 志强, additional, Paubert, Gabriel, additional, Sanchez-Portal, Miguel, additional, Kramer, Carsten, additional, Castillo, Manuel, additional, Navarro, Santiago, additional, John, David, additional, Schuster, Karl-Friedrich, additional, Johnson, Michael D., additional, Rygl, Kazi L. J., additional, Akiyama, Kazunori, additional, Alberdi, Antxon, additional, Alef, Walter, additional, Algaba, Juan Carlos, additional, Anantua, Richard, additional, Asada, Keiichi, additional, Azulay, Rebecca, additional, Bach, Uwe, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Baloković, Mislav, additional, Barrett, John, additional, Bauböck, Michi, additional, Benson, Bradford A., additional, Bintley, Dan, additional, Blundell, Raymond, additional, Bouman, Katherine L., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broderick, Avery E., additional, Broguiere, Dominique, additional, Bronzwaer, Thomas, additional, Bustamante, Sandra, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Ceccobello, Chiara, additional, Chael, Andrew, additional, Chang, Dominic O., additional, Chatterjee, Koushik, additional, Chen, Ming-Tang, additional, Chen 陈, Yongjun 永军, additional, Cheng, Xiaopeng, additional, Cho, Ilje, additional, Christian, Pierre, additional, Conroy, Nicholas S., additional, Conway, John E., additional, Crawford, Thomas M., additional, Cruz-Osorio, Alejandro, additional, Cui 崔, Yuzhu 玉竹, additional, Dahale, Rohan, additional, Davelaar, Jordy, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Dexter, Jason, additional, Dhruv, Vedant, additional, Doeleman, Sheperd S., additional, Dougal, Sean, additional, Dzib, Sergio A., additional, Emami, Razieh, additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Foschi, Marianna, additional, Fraga-Encinas, Raquel, additional, Freeman, William T., additional, Friberg, Per, additional, Fromm, Christian M., additional, Fuentes, Antonio, additional, Galison, Peter, additional, Gammie, Charles F., additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Gold, Roman, additional, Gómez, José L., additional, Gu 顾, Minfeng 敏峰, additional, Gurwell, Mark, additional, Hada, Kazuhiro, additional, Haggard, Daryl, additional, Haworth, Kari, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Heumann, Dirk, additional, Ho 何, Luis C. 子山, additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang 黄, Lei 磊, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Impellizzeri, C. M. Violette, additional, Inoue, Makoto, additional, Issaoun, Sara, additional, James, David J., additional, Jannuzi, Buell T., additional, Jeter, Britton, additional, Jiménez-Rosales, Alejandra, additional, Jorstad, Svetlana, additional, Joshi, Abhishek V., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Kawashima, Tomohisa, additional, Keating, Garrett K., additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jae-Young, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Kino, Motoki, additional, Koay, Jun Yi, additional, Kocherlakota, Prashant, additional, Kofuji, Yutaro, additional, Koyama, Shoko, additional, Krichbaum, Thomas P., additional, Kuo, Cheng-Yu, additional, La Bella, Noemi, additional, Lauer, Tod R., additional, Lee, Daeyoung, additional, Lee, Sang-Sung, additional, Leung, Po Kin, additional, Levis, Aviad, additional, Li 李, Zhiyuan 志远, additional, Lico, Rocco, additional, Lindahl, Greg, additional, Lindqvist, Michael, additional, Lisakov, Mikhail, additional, Liu 刘, Jun 俊, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Loinard, Laurent, additional, Lonsdale, Colin J., additional, MacDonald, Nicholas R., additional, Mao 毛, Jirong 基荣, additional, Marchili, Nicola, additional, Markoff, Sera, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Martí-Vidal, Iván, additional, Matsushita, Satoki, additional, Medeiros, Lia, additional, Menten, Karl M., additional, Michalik, Daniel, additional, Mizuno, Izumi, additional, Mizuno, Yosuke, additional, Moran, James M., additional, Moriyama, Kotaro, additional, Moscibrodzka, Monika, additional, Müller, Cornelia, additional, Müller, Hendrik, additional, Mus, Alejandro, additional, Musoke, Gibwa, additional, Myserlis, Ioannis, additional, Nadolski, Andrew, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Neilsen, Joey, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Nowak, Michael A., additional, Oh, Junghwan, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Paraschos, Georgios Filippos, additional, Park, Jongho, additional, Parsons, Harriet, additional, Patel, Nimesh, additional, Pesce, Dominic W., additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Pötzl, Felix M., additional, Prather, Ben, additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Pu, Hung-Yi, additional, Ramakrishnan, Venkatessh, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Roelofs, Freek, additional, Rogers, Alan, additional, Ros, Eduardo, additional, Romero-Cañizales, Cristina, additional, Roshanineshat, Arash, additional, Roy, Alan L., additional, Ruszczyk, Chet, additional, Sánchez-Argüelles, David, additional, Sasada, Mahito, additional, Satapathy, Kaushik, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schonfeld, Jonathan, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Souccar, Kamal, additional, Sun 孙, He 赫, additional, Tetarenko, Alexandra J., additional, Tiede, Paul, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Toscano, Teresa, additional, Traianou, Efthalia, additional, Trent, Tyler, additional, Trippe, Sascha, additional, Turk, Matthew, additional, van Bemmel, Ilse, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Vos, Jesse, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Weintroub, Jonathan, additional, Wex, Norbert, additional, Wielgus, Maciek, additional, Wiik, Kaj, additional, Witzel, Gunther, additional, Wondrak, Michael F., additional, Wong, George N., additional, Wu 吴, Qingwen 庆文, additional, Yadlapalli, Nitika, additional, Yamaguchi, Paul, additional, Yfantis, Aristomenis, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Younsi, Ziri, additional, Yu 于, Wei 威, additional, Yuan 袁, Feng 峰, additional, Yuan 袁, Ye-Fei 业飞, additional, Zensus, J. Anton, additional, Zhang, Shuo, additional, Zhao, Guang-Yao, additional, and Zhao 赵, Shan-Shan 杉杉, additional
Published: 2023
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39. Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes

Author: Roelofs, Freek, primary, Johnson, Michael D., additional, Chael, Andrew, additional, Janssen, Michael, additional, Wielgus, Maciek, additional, Broderick, Avery E., additional, Akiyama, Kazunori, additional, Alberdi, Antxon, additional, Alef, Walter, additional, Algaba, Juan Carlos, additional, Anantua, Richard, additional, Asada, Keiichi, additional, Azulay, Rebecca, additional, Bach, Uwe, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Baloković, Mislav, additional, Barrett, John, additional, Bauböck, Michi, additional, Benson, Bradford A., additional, Bintley, Dan, additional, Blackburn, Lindy, additional, Blundell, Raymond, additional, Bouman, Katherine L., additional, Bower, Geoffrey C., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broguiere, Dominique, additional, Bronzwaer, Thomas, additional, Bustamante, Sandra, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Ceccobello, Chiara, additional, Chan, Chi-kwan, additional, Chang, Dominic O., additional, Chatterjee, Koushik, additional, Chatterjee, Shami, additional, Chen, Ming-Tang, additional, Chen 陈, Yongjun 永军, additional, Cheng, Xiaopeng, additional, Cho, Ilje, additional, Christian, Pierre, additional, Conroy, Nicholas S., additional, Conway, John E., additional, Cordes, James M., additional, Crawford, Thomas M., additional, Crew, Geoffrey B., additional, Cruz-Osorio, Alejandro, additional, Cui 崔, Yuzhu 玉竹, additional, Dahale, Rohan, additional, Davelaar, Jordy, additional, De Laurentis, Mariafelicia, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Desvignes, Gregory, additional, Dexter, Jason, additional, Dhruv, Vedant, additional, Doeleman, Sheperd S., additional, Dougal, Sean, additional, Dzib, Sergio A., additional, Eatough, Ralph P., additional, Emami, Razieh, additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Foschi, Marianna, additional, Fraga-Encinas, Raquel, additional, Freeman, William T., additional, Friberg, Per, additional, Fromm, Christian M., additional, Fuentes, Antonio, additional, Galison, Peter, additional, Gammie, Charles F., additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Goddi, Ciriaco, additional, Gold, Roman, additional, Gómez-Ruiz, Arturo I., additional, Gómez, José L., additional, Gu 顾, Minfeng 敏峰, additional, Gurwell, Mark, additional, Hada, Kazuhiro, additional, Haggard, Daryl, additional, Haworth, Kari, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Heumann, Dirk, additional, Ho 何, Luis C. 子山, additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang 黄, Lei 磊, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Impellizzeri, C. M. Violette, additional, Inoue, Makoto, additional, Issaoun, Sara, additional, James, David J., additional, Jannuzi, Buell T., additional, Jeter, Britton, additional, Jiang 江, Wu 悟, additional, Jiménez-Rosales, Alejandra, additional, Jorstad, Svetlana, additional, Joshi, Abhishek V., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Karuppusamy, Ramesh, additional, Kawashima, Tomohisa, additional, Keating, Garrett K., additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jae-Young, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Kino, Motoki, additional, Koay, Jun Yi, additional, Kocherlakota, Prashant, additional, Kofuji, Yutaro, additional, Koch, Patrick M., additional, Koyama, Shoko, additional, Kramer, Carsten, additional, Kramer, Joana A., additional, Kramer, Michael, additional, Krichbaum, Thomas P., additional, Kuo, Cheng-Yu, additional, La Bella, Noemi, additional, Lauer, Tod R., additional, Lee, Daeyoung, additional, Lee, Sang-Sung, additional, Leung, Po Kin, additional, Levis, Aviad, additional, Li 李, Zhiyuan 志远, additional, Lico, Rocco, additional, Lindahl, Greg, additional, Lindqvist, Michael, additional, Lisakov, Mikhail, additional, Liu 刘, Jun 俊, additional, Liu, Kuo, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Loinard, Laurent, additional, Lonsdale, Colin J., additional, Lowitz, Amy E., additional, Lu 路, Ru-Sen 如森, additional, MacDonald, Nicholas R., additional, Mao 毛, Jirong 基荣, additional, Marchili, Nicola, additional, Markoff, Sera, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Martí-Vidal, Iván, additional, Matsushita, Satoki, additional, Matthews, Lynn D., additional, Medeiros, Lia, additional, Menten, Karl M., additional, Michalik, Daniel, additional, Mizuno, Izumi, additional, Mizuno, Yosuke, additional, Moran, James M., additional, Moriyama, Kotaro, additional, Moscibrodzka, Monika, additional, Mulaudzi, Wanga, additional, Müller, Cornelia, additional, Müller, Hendrik, additional, Mus, Alejandro, additional, Musoke, Gibwa, additional, Myserlis, Ioannis, additional, Nadolski, Andrew, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Fuentes, Santiago Navarro, additional, Neilsen, Joey, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Nowak, Michael A., additional, Oh, Junghwan, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Paraschos, Georgios Filippos, additional, Park, Jongho, additional, Parsons, Harriet, additional, Patel, Nimesh, additional, Pen, Ue-Li, additional, Pesce, Dominic W., additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Pötzl, Felix M., additional, Prather, Ben, additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Pu, Hung-Yi, additional, Ramakrishnan, Venkatessh, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Raymond, Alexander W., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Rogers, Alan, additional, Romero-Cañizales, Cristina, additional, Ros, Eduardo, additional, Roshanineshat, Arash, additional, Rottmann, Helge, additional, Roy, Alan L., additional, Ruiz, Ignacio, additional, Ruszczyk, Chet, additional, Rygl, Kazi L. J., additional, Sánchez, Salvador, additional, Sánchez-Argüelles, David, additional, Sánchez-Portal, Miguel, additional, Sasada, Mahito, additional, Satapathy, Kaushik, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schonfeld, Jonathan, additional, Schuster, Karl-Friedrich, additional, Shao, Lijing, additional, Shen 沈, Zhiqiang 志强, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Sosapanta Salas, León David, additional, Souccar, Kamal, additional, Sun 孙, He 赫, additional, Tazaki, Fumie, additional, Tetarenko, Alexandra J., additional, Tiede, Paul, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Torne, Pablo, additional, Toscano, Teresa, additional, Traianou, Efthalia, additional, Trent, Tyler, additional, Trippe, Sascha, additional, Turk, Matthew, additional, van Bemmel, Ilse, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Vos, Jesse, additional, Wagner, Jan, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Washington, Jasmin E., additional, Weintroub, Jonathan, additional, Wharton, Robert, additional, Wiik, Kaj, additional, Witzel, Gunther, additional, Wondrak, Michael F., additional, Wong, George N., additional, Wu 吴, Qingwen 庆文, additional, Yadlapalli, Nitika, additional, Yamaguchi, Paul, additional, Yfantis, Aristomenis, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Younsi, Ziri, additional, Yu 于, Wei 威, additional, Yuan 袁, Feng 峰, additional, Yuan 袁, Ye-Fei 业飞, additional, Zensus, J. Anton, additional, Zhang, Shuo, additional, Zhao, Guang-Yao, additional, and Zhao 赵, Shan-Shan 杉杉, additional
Published: 2023
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40. Nature of 60 micron emission in 3C47, 3C207 and 3C334

Author: van Bemmel, Ilse M., Barthel, Peter D., and Yun, Min S.
Subjects: Astrophysics
Abstract: We try to explain the unusually high far-infrared emission seen by IRAS in the double-lobed radio-loud quasars 3C47, 3C207 and 3C334. High resolution cm--mm observations were carried out to determine their radio core spectra, which are subsequently extrapolated to the far-infrared in order to determine the strength of the synchrotron far-infrared emission. The extrapolated flux densities being considerably lower than the observed values, a significant nonthermal far-infrared component is unlikely in the case of 3C47 and 3C334. However, this component could be responsible for the far-infrared brightness of 3C207. Our analysis demonstrates that nonthermal emission cannot readily account for the difference between quasars and radio galaxies in the amount of their far-infrared luminosity. On the other hand, a significant role for this mechanism is likely; full sampling of the mm-submm spectral energy distributions is needed to address the issue quantitatively., Comment: 7 pages, incl. 3 figures; accepted for publication in A&A
Published: 1998

41. Comparison of Polarized Radiative Transfer Codes Used by the EHT Collaboration

Author: Prather, Ben S., primary, Dexter, Jason, additional, Moscibrodzka, Monika, additional, Pu, Hung-Yi, additional, Bronzwaer, Thomas, additional, Davelaar, Jordy, additional, Younsi, Ziri, additional, Gammie, Charles F., additional, Gold, Roman, additional, Wong, George N., additional, Akiyama, Kazunori, additional, Alberdi, Antxon, additional, Alef, Walter, additional, Algaba, Juan Carlos, additional, Anantua, Richard, additional, Asada, Keiichi, additional, Azulay, Rebecca, additional, Bach, Uwe, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Baloković, Mislav, additional, Barrett, John, additional, Bauböck, Michi, additional, Benson, Bradford A., additional, Bintley, Dan, additional, Blackburn, Lindy, additional, Blundell, Raymond, additional, Bouman, Katherine L., additional, Bower, Geoffrey C., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broderick, Avery E., additional, Broguiere, Dominique, additional, Bustamante, Sandra, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Ceccobello, Chiara, additional, Chael, Andrew, additional, Chan, Chi-kwan, additional, Chang, Dominic O., additional, Chatterjee, Koushik, additional, Chatterjee, Shami, additional, Chen, Ming-Tang, additional, Chen, Yongjun, additional, Cheng, Xiaopeng, additional, Cho, Ilje, additional, Christian, Pierre, additional, Conroy, Nicholas S., additional, Conway, John E., additional, Cordes, James M., additional, Crawford, Thomas M., additional, Crew, Geoffrey B., additional, Cruz-Osorio, Alejandro, additional, Cui, Yuzhu, additional, De Laurentis, Mariafelicia, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Desvignes, Gregory, additional, Dhruv, Vedant, additional, Doeleman, Sheperd S., additional, Dougal, Sean, additional, Dzib, Sergio A., additional, Eatough, Ralph P., additional, Emami, Razieh, additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Fraga-Encinas, Raquel, additional, Freeman, William T., additional, Friberg, Per, additional, Fromm, Christian M., additional, Fuentes, Antonio, additional, Galison, Peter, additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Goddi, Ciriaco, additional, Gómez-Ruiz, Arturo I., additional, Gómez, José L., additional, Gu, Minfeng, additional, Gurwell, Mark, additional, Hada, Kazuhiro, additional, Haggard, Daryl, additional, Haworth, Kari, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Heumann, Dirk, additional, Ho, Luis C., additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang, Lei, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Impellizzeri, C. M. Violette, additional, Inoue, Makoto, additional, Issaoun, Sara, additional, James, David J., additional, Jannuzi, Buell T., additional, Janssen, Michael, additional, Jeter, Britton, additional, Jiang, Wu, additional, Jiménez-Rosales, Alejandra, additional, Johnson, Michael D., additional, Jorstad, Svetlana, additional, Joshi, Abhishek V., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Karuppusamy, Ramesh, additional, Kawashima, Tomohisa, additional, Keating, Garrett K., additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jae-Young, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Kino, Motoki, additional, Koay, Jun Yi, additional, Kocherlakota, Prashant, additional, Kofuji, Yutaro, additional, Koyama, Shoko, additional, Kramer, Carsten, additional, Kramer, Michael, additional, Krichbaum, Thomas P., additional, Kuo, Cheng-Yu, additional, La Bella, Noemi, additional, Lauer, Tod R., additional, Lee, Daeyoung, additional, Lee, Sang-Sung, additional, Leung, Po Kin, additional, Levis, Aviad, additional, Li, Zhiyuan, additional, Lico, Rocco, additional, Lindahl, Greg, additional, Lindqvist, Michael, additional, Lisakov, Mikhail, additional, Liu, Jun, additional, Liu, Kuo, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Loinard, Laurent, additional, Lonsdale, Colin J., additional, Lu, Ru-Sen, additional, MacDonald, Nicholas R., additional, Mao, Jirong, additional, Marchili, Nicola, additional, Markoff, Sera, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Martí-Vidal, Iván, additional, Matsushita, Satoki, additional, Matthews, Lynn D., additional, Medeiros, Lia, additional, Menten, Karl M., additional, Michalik, Daniel, additional, Mizuno, Izumi, additional, Mizuno, Yosuke, additional, Moran, James M., additional, Moriyama, Kotaro, additional, Müller, Cornelia, additional, Mus, Alejandro, additional, Musoke, Gibwa, additional, Myserlis, Ioannis, additional, Nadolski, Andrew, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Fuentes, Santiago Navarro, additional, Neilsen, Joey, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Nowak, Michael A., additional, Oh, Junghwan, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Paraschos, Georgios Filippos, additional, Park, Jongho, additional, Parsons, Harriet, additional, Patel, Nimesh, additional, Pen, Ue-Li, additional, Pesce, Dominic W., additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Pötzl, Felix M., additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Ramakrishnan, Venkatessh, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Raymond, Alexander W., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Roelofs, Freek, additional, Rogers, Alan, additional, Ros, Eduardo, additional, Romero-Cañizales, Cristina, additional, Roshanineshat, Arash, additional, Rottmann, Helge, additional, Roy, Alan L., additional, Ruiz, Ignacio, additional, Ruszczyk, Chet, additional, Rygl, Kazi L. J., additional, Sánchez, Salvador, additional, Sánchez-Argüelles, David, additional, Sánchez-Portal, Miguel, additional, Sasada, Mahito, additional, Satapathy, Kaushik, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schonfeld, Jonathan, additional, Schuster, Karl-Friedrich, additional, Shao, Lijing, additional, Shen, Zhiqiang, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Souccar, Kamal, additional, Sun, He, additional, Tazaki, Fumie, additional, Tetarenko, Alexandra J., additional, Tiede, Paul, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Torne, Pablo, additional, Traianou, Efthalia, additional, Trent, Tyler, additional, Trippe, Sascha, additional, Turk, Matthew, additional, van Bemmel, Ilse, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Vos, Jesse, additional, Wagner, Jan, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Weintroub, Jonathan, additional, Wex, Norbert, additional, Wharton, Robert, additional, Wielgus, Maciek, additional, Wiik, Kaj, additional, Witzel, Gunther, additional, Wondrak, Michael F., additional, Wu, Qingwen, additional, Yamaguchi, Paul, additional, Yfantis, Aristomenis, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Yu, Wei, additional, Yuan, Feng, additional, Yuan, Ye-Fei, additional, Zensus, J. Anton, additional, Zhang, Shuo, additional, Zhao, Guang-Yao, additional, and Zhao, Shan-Shan, additional
Published: 2023
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42. Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes

Author: Roelofs, Freek, Johnson, Michael D., Chael, Andrew, Janssen, Michael, Wielgus, Maciek, Broderick, Avery E., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chan, Chi-kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Joana A., Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lowitz, Amy E., Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Mulaudzi, Wanga, Müller, Cornelia, Müller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Rogers, Alan, Romero-Cañizales, Cristina, Ros, Eduardo, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sosapanta Salas, León David, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Washington, Jasmin E., Weintroub, Jonathan, Wharton, Robert, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, Zhao, Shan-Shan, Roelofs, Freek, Johnson, Michael D., Chael, Andrew, Janssen, Michael, Wielgus, Maciek, Broderick, Avery E., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chan, Chi-kwan, Chang, Dominic O., Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Dahale, Rohan, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Foschi, Marianna, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Joana A., Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, La Bella, Noemi, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lowitz, Amy E., Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Medeiros, Lia, Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Mulaudzi, Wanga, Müller, Cornelia, Müller, Hendrik, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Özel, Feryal, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Psaltis, Dimitrios, Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Rogers, Alan, Romero-Cañizales, Cristina, Ros, Eduardo, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sosapanta Salas, León David, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Toscano, Teresa, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Washington, Jasmin E., Weintroub, Jonathan, Wharton, Robert, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yadlapalli, Nitika, Yamaguchi, Paul, Yfantis, Aristomenis, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yu, Wei, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhang, Shuo, Zhao, Guang-Yao, and Zhao, Shan-Shan
Abstract: The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*. Polarimetric data from these observations contain a wealth of information on the black hole and accretion flow properties. In this work, we develop polarimetric geometric modeling methods for mm-VLBI data, focusing on approaches that fit data products with differing degrees of invariance to broad classes of calibration errors. We establish a fitting procedure using a polarimetric “m-ring” model to approximate the image structure near a black hole. By fitting this model to synthetic EHT data from general relativistic magnetohydrodynamic models, we show that the linear and circular polarization structure can be successfully approximated with relatively few model parameters. We then fit this model to EHT observations of M87* taken in 2017. In total intensity and linear polarization, the m-ring fits are consistent with previous results from imaging methods. In circular polarization, the m-ring fits indicate the presence of event-horizon-scale circular polarization structure, with a persistent dipolar asymmetry and orientation across several days. The same structure was recovered independently of observing band, used data products, and model assumptions. Despite this broad agreement, imaging methods do not produce similarly consistent results. Our circular polarization results, which imposed additional assumptions on the source structure, should thus be interpreted with some caution. Polarimetric geometric modeling provides a useful and powerful method to constrain the properties of horizon-scale polarized emission, particularly for sparse arrays like the EHT.
Published: 2023

43. The Event Horizon Telescope Image of the Quasar NRAO 530

Author: Jorstad, Svetlana, primary, Wielgus, Maciek, additional, Lico, Rocco, additional, Issaoun, Sara, additional, Broderick, Avery E., additional, Pesce, Dominic W., additional, Liu, Jun, additional, Zhao, Guang-Yao, additional, Krichbaum, Thomas P., additional, Blackburn, Lindy, additional, Chan, Chi-kwan, additional, Janssen, Michael, additional, Ramakrishnan, Venkatessh, additional, Akiyama, Kazunori, additional, Alberdi, Antxon, additional, Algaba, Juan Carlos, additional, Bouman, Katherine L., additional, Cho, Ilje, additional, Fuentes, Antonio, additional, Gómez, José L., additional, Gurwell, Mark, additional, Johnson, Michael D., additional, Kim, Jae-Young, additional, Lu, Ru-Sen, additional, Martí-Vidal, Iván, additional, Moscibrodzka, Monika, additional, Pötzl, Felix M., additional, Traianou, Efthalia, additional, van Bemmel, Ilse, additional, Alef, Walter, additional, Anantua, Richard, additional, Asada, Keiichi, additional, Azulay, Rebecca, additional, Bach, Uwe, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Baloković, Mislav, additional, Barrett, John, additional, Bauböck, Michi, additional, Benson, Bradford A., additional, Bintley, Dan, additional, Blundell, Raymond, additional, Bower, Geoffrey C., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broguiere, Dominique, additional, Bronzwaer, Thomas, additional, Bustamante, Sandra, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Ceccobello, Chiara, additional, Chael, Andrew, additional, Chatterjee, Koushik, additional, Chatterjee, Shami, additional, Chen, Ming-Tang, additional, Chen, Yongjun, additional, Cheng, Xiaopeng, additional, Christian, Pierre, additional, Conroy, Nicholas S., additional, Conway, John E., additional, Cordes, James M., additional, Crawford, Thomas M., additional, Crew, Geoffrey B., additional, Cruz-Osorio, Alejandro, additional, Cui, Yuzhu, additional, Davelaar, Jordy, additional, De Laurentis, Mariafelicia, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Desvignes, Gregory, additional, Dexter, Jason, additional, Dhruv, Vedant, additional, Doeleman, Sheperd S., additional, Dougal, Sean, additional, Dzib, Sergio A., additional, Eatough, Ralph P., additional, Emami, Razieh, additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Fraga-Encinas, Raquel, additional, Freeman, William T., additional, Friberg, Per, additional, Fromm, Christian M., additional, Galison, Peter, additional, Gammie, Charles F., additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Goddi, Ciriaco, additional, Gold, Roman, additional, Gómez-Ruiz, Arturo I., additional, Gu, Minfeng, additional, Hada, Kazuhiro, additional, Haggard, Daryl, additional, Haworth, Kari, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Heumann, Dirk, additional, Ho, Luis C., additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang, Lei, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Impellizzeri, C. M. Violette, additional, Inoue, Makoto, additional, James, David J., additional, Jannuzi, Buell T., additional, Jeter, Britton, additional, Jiang, Wu, additional, Jiménez-Rosales, Alejandra, additional, Joshi, Abhishek V., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Karuppusamy, Ramesh, additional, Kawashima, Tomohisa, additional, Keating, Garrett K., additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Kino, Motoki, additional, Koay, Jun Yi, additional, Kocherlakota, Prashant, additional, Kofuji, Yutaro, additional, Koyama, Shoko, additional, Kramer, Carsten, additional, Kramer, Michael, additional, Kuo, Cheng-Yu, additional, La Bella, Noemi, additional, Lauer, Tod R., additional, Lee, Daeyoung, additional, Lee, Sang-Sung, additional, Leung, Po Kin, additional, Levis, Aviad, additional, Li, Zhiyuan, additional, Lindahl, Greg, additional, Lindqvist, Michael, additional, Lisakov, Mikhail, additional, Liu, Kuo, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Loinard, Laurent, additional, Lonsdale, Colin J., additional, MacDonald, Nicholas R., additional, Mao, Jirong, additional, Marchili, Nicola, additional, Markoff, Sera, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Matsushita, Satoki, additional, Matthews, Lynn D., additional, Medeiros, Lia, additional, Menten, Karl M., additional, Michalik, Daniel, additional, Mizuno, Izumi, additional, Mizuno, Yosuke, additional, Moran, James M., additional, Moriyama, Kotaro, additional, Müller, Cornelia, additional, Mus, Alejandro, additional, Musoke, Gibwa, additional, Myserlis, Ioannis, additional, Nadolski, Andrew, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Fuentes, Santiago Navarro, additional, Neilsen, Joey, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Nowak, Michael A., additional, Oh, Junghwan, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Paraschos, Georgios Filippos, additional, Park, Jongho, additional, Parsons, Harriet, additional, Patel, Nimesh, additional, Pen, Ue-Li, additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Prather, Ben, additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Pu, Hung-Yi, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Raymond, Alexander W., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Roelofs, Freek, additional, Rogers, Alan, additional, Ros, Eduardo, additional, Romero-Cañizales, Cristina, additional, Roshanineshat, Arash, additional, Rottmann, Helge, additional, Roy, Alan L., additional, Ruiz, Ignacio, additional, Ruszczyk, Chet, additional, Rygl, Kazi L. J., additional, Sánchez, Salvador, additional, Sánchez-Argüelles, David, additional, Sánchez-Portal, Miguel, additional, Sasada, Mahito, additional, Satapathy, Kaushik, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schonfeld, Jonathan, additional, Schuster, Karl-Friedrich, additional, Shao, Lijing, additional, Shen, Zhiqiang, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Souccar, Kamal, additional, Sun, He, additional, Tazaki, Fumie, additional, Tetarenko, Alexandra J., additional, Tiede, Paul, additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Torne, Pablo, additional, Trent, Tyler, additional, Trippe, Sascha, additional, Turk, Matthew, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Vos, Jesse, additional, Wagner, Jan, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Weintroub, Jonathan, additional, Wex, Norbert, additional, Wharton, Robert, additional, Wiik, Kaj, additional, Witzel, Gunther, additional, Wondrak, Michael F., additional, Wong, George N., additional, Wu, Qingwen, additional, Yamaguchi, Paul, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Younsi, Ziri, additional, Yuan, Feng, additional, Yuan, Ye-Fei, additional, Zensus, J. Anton, additional, Zhang, Shuo, additional, and Zhao, Shan-Shan, additional
Published: 2023
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44. A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

Author: Fallows Richard A., Forte Biagio, Astin Ivan, Allbrook Tom, Arnold Alex, Wood Alan, Dorrian Gareth, Mevius Maaijke, Rothkaehl Hanna, Matyjasiak Barbara, Krankowski Andrzej, Anderson James M., Asgekar Ashish, Avruch I. Max, Bentum Mark, Bisi Mario M., Butcher Harvey R., Ciardi Benedetta, Dabrowski Bartosz, Damstra Sieds, de Gasperin Francesco, Duscha Sven, Eislöffel Jochen, Franzen Thomas M.O., Garrett Michael A., Grießmeier Jean-Matthias, Gunst André W., Hoeft Matthias, Hörandel Jörg R., Iacobelli Marco, Intema Huib T., Koopmans Leon V.E., Maat Peter, Mann Gottfried, Nelles Anna, Paas Harm, Pandey Vishambhar N., Reich Wolfgang, Rowlinson Antonia, Ruiter Mark, Schwarz Dominik J., Serylak Maciej, Shulevski Aleksander, Smirnov Oleg M., Soida Marian, Steinmetz Matthias, Thoudam Satyendra, Toribio M. Carmen, van Ardenne Arnold, van Bemmel Ilse M., van der Wiel Matthijs H.D., van Haarlem Michiel P., Vermeulen René C., Vocks Christian, Wijers Ralph A.M.J., Wucknitz Olaf, Zarka Philippe, and Zucca Pietro
Subjects: ionospheric scintillation, travelling ionospheric disturbances, instability mechanisms, Meteorology. Climatology, QC851-999
Abstract: This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18–19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10–80 MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR “core” reveals two different velocities in the scintillation pattern: a primary velocity of ~20–40 ms−1 with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110 ms−1 with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller-scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported.
Published: 2020
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45. CASA on the Fringe—Development of VLBI Processing Capabilities for CASA

Author: van Bemmel, Ilse M., primary, Kettenis, Mark, additional, Small, Des, additional, Janssen, Michael, additional, Moellenbrock, George A., additional, Petry, Dirk, additional, Goddi, Ciriaco, additional, Linford, Justin D., additional, Rygl, Kazi L. J., additional, Liuzzo, Elisabetta, additional, Marcote, Benito, additional, Bayandina, Olga S., additional, Schweighart, Neal, additional, Verkouter, Marjolein, additional, Keimpema, Aard, additional, Szomoru, Arpad, additional, and van Langevelde, Huib Jan, additional
Published: 2022
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46. LOFAR calibration and wide-field imaging

Author: Tasse, Cyril, van Diepen, Ger, van der Tol, Sebastiaan, van Weeren, Reinout J., van Zwieten, Joris E., Batejat, Fabien, Bhatnagar, Sanjay, van Bemmel, Ilse, Bîrzan, Laura, Bonafede, Annalisa, Conway, John, Ferrari, Chiara, De Gasperin, Francesco, Golap, Kumar, Heald, George, Jackson, Neal, Macario, Giulia, McKean, John, Mohan, Niruj, Orrù, Emanuela, Pizzo, Roberto, Rafferty, David, Rau, Urvashi, Röttgering, Huub, and Shulevski, Aleksandar
Published: 2012
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47. Resolving the Inner Parsec of the Blazar J1924–2914 with the Event Horizon Telescope

Author: Issaoun, Sara, primary, Wielgus, Maciek, additional, Jorstad, Svetlana, additional, Krichbaum, Thomas P., additional, Blackburn, Lindy, additional, Janssen, Michael, additional, Chan, Chi-kwan, additional, Pesce, Dominic W., additional, Gómez, José L., additional, Akiyama, Kazunori, additional, Mościbrodzka, Monika, additional, Martí-Vidal, Iván, additional, Chael, Andrew, additional, Lico, Rocco, additional, Liu, Jun, additional, Ramakrishnan, Venkatessh, additional, Lisakov, Mikhail, additional, Fuentes, Antonio, additional, Zhao, Guang-Yao, additional, Moriyama, Kotaro, additional, Broderick, Avery E., additional, Tiede, Paul, additional, MacDonald, Nicholas R., additional, Mizuno, Yosuke, additional, Traianou, Efthalia, additional, Loinard, Laurent, additional, Davelaar, Jordy, additional, Gurwell, Mark, additional, Lu, Ru-Sen, additional, Alberdi, Antxon, additional, Alef, Walter, additional, Algaba, Juan Carlos, additional, Anantua, Richard, additional, Asada, Keiichi, additional, Azulay, Rebecca, additional, Bach, Uwe, additional, Baczko, Anne-Kathrin, additional, Ball, David, additional, Baloković, Mislav, additional, Barrett, John, additional, Bauböck, Michi, additional, Benson, Bradford A., additional, Bintley, Dan, additional, Blundell, Raymond, additional, Boland, Wilfred, additional, Bouman, Katherine L., additional, Bower, Geoffrey C., additional, Boyce, Hope, additional, Bremer, Michael, additional, Brinkerink, Christiaan D., additional, Brissenden, Roger, additional, Britzen, Silke, additional, Broguiere, Dominique, additional, Bronzwaer, Thomas, additional, Bustamante, Sandra, additional, Byun, Do-Young, additional, Carlstrom, John E., additional, Ceccobello, Chiara, additional, Chatterjee, Koushik, additional, Chatterjee, Shami, additional, Chen, Ming-Tang, additional, Chen, Yongjun, additional, Cho, Ilje, additional, Christian, Pierre, additional, Conroy, Nicholas S., additional, Conway, John E., additional, Cordes, James M., additional, Crawford, Thomas M., additional, Crew, Geoffrey B., additional, Cruz-Osorio, Alejandro, additional, Cui, Yuzhu, additional, Laurentis, Mariafelicia De, additional, Deane, Roger, additional, Dempsey, Jessica, additional, Desvignes, Gregory, additional, Dexter, Jason, additional, Doeleman, Sheperd S., additional, Dhruv, Vedant, additional, Dzib Quijano, Sergio Abraham, additional, Eatough, Ralph P., additional, Emami, Razieh, additional, Falcke, Heino, additional, Farah, Joseph, additional, Fish, Vincent L., additional, Fomalont, Ed, additional, Ford, H. Alyson, additional, Fraga-Encinas, Raquel, additional, Freeman, William T., additional, Friberg, Per, additional, Fromm, Christian M., additional, Galison, Peter, additional, Gammie, Charles F., additional, García, Roberto, additional, Gentaz, Olivier, additional, Georgiev, Boris, additional, Goddi, Ciriaco, additional, Gold, Roman, additional, Gómez-Ruiz, Arturo I., additional, Gu, Minfeng, additional, Hada, Kazuhiro, additional, Haggard, Daryl, additional, Hecht, Michael H., additional, Hesper, Ronald, additional, Ho, Luis C., additional, Ho, Paul, additional, Honma, Mareki, additional, Huang, Chih-Wei L., additional, Huang, Lei, additional, Hughes, David H., additional, Ikeda, Shiro, additional, Impellizzeri, C. M. Violette, additional, Inoue, Makoto, additional, James, David J., additional, Jannuzi, Buell T., additional, Jeter, Britton, additional, Jiang, Wu, additional, Jimenez-Rosales, Alejandra, additional, Johnson, Michael D., additional, Joshi, Abhishek V., additional, Jung, Taehyun, additional, Karami, Mansour, additional, Karuppusamy, Ramesh, additional, Kawashima, Tomohisa, additional, Keating, Garrett K., additional, Kettenis, Mark, additional, Kim, Dong-Jin, additional, Kim, Jae-Young, additional, Kim, Jongsoo, additional, Kim, Junhan, additional, Kino, Motoki, additional, Koay, Jun Yi, additional, Kocherlakota, Prashant, additional, Kofuji, Yutaro, additional, Koch, Patrick M., additional, Koyama, Shoko, additional, Kramer, Carsten, additional, Kramer, Michael, additional, Kuo, Cheng-Yu, additional, Bella, Noemi La, additional, Lauer, Tod R., additional, Lee, Daeyoung, additional, Lee, Sang-Sung, additional, Leung, Po Kin, additional, Levis, Aviad, additional, Li, Zhiyuan, additional, Lindahl, Greg, additional, Lindqvist, Michael, additional, Liu, Kuo, additional, Liuzzo, Elisabetta, additional, Lo, Wen-Ping, additional, Lobanov, Andrei P., additional, Lonsdale, Colin, additional, Mao, Jirong, additional, Marchili, Nicola, additional, Markoff, Sera, additional, Marrone, Daniel P., additional, Marscher, Alan P., additional, Matsushita, Satoki, additional, Matthews, Lynn D., additional, Medeiros, Lia, additional, Menten, Karl M., additional, Michalik, Daniel, additional, Mizuno, Izumi, additional, Moran, James M., additional, Müller, Cornelia, additional, Mus, Alejandro, additional, Musoke, Gibwa, additional, Myserlis, Ioannis, additional, Nadolski, Andrew, additional, Nagai, Hiroshi, additional, Nagar, Neil M., additional, Nakamura, Masanori, additional, Narayan, Ramesh, additional, Narayanan, Gopal, additional, Natarajan, Iniyan, additional, Nathanail, Antonios, additional, Neilsen, Joey, additional, Neri, Roberto, additional, Ni, Chunchong, additional, Noutsos, Aristeidis, additional, Nowak, Michael A., additional, Oh, Junghwan, additional, Okino, Hiroki, additional, Olivares, Héctor, additional, Ortiz-León, Gisela N., additional, Oyama, Tomoaki, additional, Özel, Feryal, additional, Palumbo, Daniel C. M., additional, Paraschos, Georgios Filippos, additional, Park, Jongho, additional, Parsons, Harriet, additional, Patel, Nimesh, additional, Pen, Ue-Li, additional, Piétu, Vincent, additional, Plambeck, Richard, additional, PopStefanija, Aleksandar, additional, Porth, Oliver, additional, Pötzl, Felix M., additional, Prather, Ben, additional, Preciado-López, Jorge A., additional, Psaltis, Dimitrios, additional, Pu, Hung-Yi, additional, Rao, Ramprasad, additional, Rawlings, Mark G., additional, Raymond, Alexander W., additional, Rezzolla, Luciano, additional, Ricarte, Angelo, additional, Ripperda, Bart, additional, Roelofs, Freek, additional, Rogers, Alan, additional, Ros, Eduardo, additional, Romero-Canizales, Cristina, additional, Roshanineshat, Arash, additional, Rottmann, Helge, additional, Roy, Alan L., additional, Ruiz, Ignacio, additional, Ruszczyk, Chet, additional, Rygl, Kazi L. J., additional, Sánchez, Salvador, additional, Sánchez-Arguelles, David, additional, Sanchez-Portal, Miguel, additional, Sasada, Mahito, additional, Satapathy, Kaushik, additional, Savolainen, Tuomas, additional, Schloerb, F. Peter, additional, Schuster, Karl-Friedrich, additional, Shao, Lijing, additional, Shen, Zhiqiang, additional, Small, Des, additional, Sohn, Bong Won, additional, SooHoo, Jason, additional, Souccar, Kamal, additional, Sun, He, additional, Tazaki, Fumie, additional, Tetarenko, Alexandra J., additional, Tilanus, Remo P. J., additional, Titus, Michael, additional, Torne, Pablo, additional, Trent, Tyler, additional, Trippe, Sascha, additional, van Bemmel, Ilse, additional, van Langevelde, Huib Jan, additional, van Rossum, Daniel R., additional, Vos, Jesse, additional, Wagner, Jan, additional, Ward-Thompson, Derek, additional, Wardle, John, additional, Weintroub, Jonathan, additional, Wex, Norbert, additional, Wharton, Robert, additional, Wiik, Kaj, additional, Witzel, Gunther, additional, Wondrak, Michael, additional, Wong, George N., additional, Wu, Qingwen, additional, Yamaguchi, Paul, additional, Yoon, Doosoo, additional, Young, André, additional, Young, Ken, additional, Younsi, Ziri, additional, Yuan, Feng, additional, Yuan, Ye-Fei, additional, Zensus, J. Anton, additional, Zhang, Shuo, additional, and Zhao, Shan-Shan, additional
Published: 2022
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48. The science case and challenges of space-borne sub-millimeter interferometry

Author: Gurvits, Leonid I., primary, Paragi, Zsolt, additional, Amils, Ricardo I., additional, van Bemmel, Ilse, additional, Boven, Paul, additional, Casasola, Viviana, additional, Conway, John, additional, Davelaar, Jordy, additional, Díez-González, M. Carmen, additional, Falcke, Heino, additional, Fender, Rob, additional, Frey, Sándor, additional, Fromm, Christian M., additional, Gallego-Puyol, Juan D., additional, García-Miró, Cristina, additional, Garrett, Michael A., additional, Giroletti, Marcello, additional, Goddi, Ciriaco, additional, Gómez, José L., additional, van der Gucht, Jeffrey, additional, Guirado, José Carlos, additional, Haiman, Zoltán, additional, Helmich, Frank, additional, Hudson, Ben, additional, Humphreys, Elizabeth, additional, Impellizzeri, Violette, additional, Janssen, Michael, additional, Johnson, Michael D., additional, Kovalev, Yuri Y., additional, Kramer, Michael, additional, Lindqvist, Michael, additional, Linz, Hendrik, additional, Liuzzo, Elisabetta, additional, Lobanov, Andrei P., additional, López-Fernández, Isaac, additional, Malo-Gómez, Inmaculada, additional, Masania, Kunal, additional, Mizuno, Yosuke, additional, Plavin, Alexander V., additional, Rajan, Raj T., additional, Rezzolla, Luciano, additional, Roelofs, Freek, additional, Ros, Eduardo, additional, Rygl, Kazi L.J., additional, Savolainen, Tuomas, additional, Schuster, Karl, additional, Venturi, Tiziana, additional, Verkouter, Marjolein, additional, de Vicente, Pablo, additional, Visser, Pieter N.A.M., additional, Wiedner, Martina C., additional, Wielgus, Maciek, additional, Wiik, Kaj, additional, and Zensus, J. Anton, additional
Published: 2022
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49. The Variability of the Black Hole Image in M87 at the Dynamical Timescale

Author: Satapathy, Kaushik, Psaltis, Dimitrios, Özel, Feryal, Medeiros, Lia, Dougall, Sean T., Chan, Chi-Kwan, Wielgus, Maciek, Prather, Ben S., Wong, George N., Gammie, Charles F., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamente, Sandra, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph P., Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Müller, Cornelia, Mejías, Alejandro Mus, Musoke, Gibwa, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wiik, Kaj, Wu, Qingwen, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, Zhao, Shan-Shan, Satapathy, Kaushik, Psaltis, Dimitrios, Özel, Feryal, Medeiros, Lia, Dougall, Sean T., Chan, Chi-Kwan, Wielgus, Maciek, Prather, Ben S., Wong, George N., Gammie, Charles F., Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Boland, Wilfred, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broderick, Avery E., Broguiere, Dominique, Bronzwaer, Thomas, Bustamente, Sandra, Byun, Do-Young, Carlstrom, John E., Chael, Andrew, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cho, Ilje, Christian, Pierre, Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Doeleman, Sheperd S., Eatough, Ralph P., Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, García, Roberto, Gentaz, Olivier, Georgiev, Boris, Goddi, Ciriaco, Gold, Roman, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Hecht, Michael H., Hesper, Ronald, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jimenez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Lauer, Tod R., Lee, Sang-Sung, Levis, Aviad, Li, Yan-Rong, Li, Zhiyuan, Lindqvist, Michael, Lico, Rocco, Lindahl, Greg, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin, Lu, Ru-Sen, MacDonald, Nicholas R., Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Menten, Karl M., Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moriyama, Kotaro, Moscibrodzka, Monika, Müller, Cornelia, Mejías, Alejandro Mus, Musoke, Gibwa, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Neilsen, Joey, Neri, Roberto, Ni, Chunchong, Noutsos, Aristeidis, Nowak, Michael A., Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C. M., Park, Jongho, Patel, Nimesh, Pen, Ue-Li, Pesce, Dominic W., Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Rose, Mel, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Arguelles, David, Sasada, Mahito, Savolainen, Tuomas, Schloerb, F. Peter, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tiede, Paul, Tilanus, Remo P. J., Titus, Michael, Toma, Kenji, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wiik, Kaj, Wu, Qingwen, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, and Zhao, Shan-Shan
Abstract: The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5–61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of ∼3°–5°. The only triangles that exhibit substantially higher variability (∼90°–180°) are the ones with baselines that cross the visibility amplitude minima on the u–v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas.
Published: 2022

50. Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI

Author: Broderick, Avery E., Gold, Roman, Georgiev, Boris, Pesce, Dominic W., Tiede, Paul, Ni, Chunchong, Moriyama, Kotaro, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chan, Chi-kwan, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Goddi, Ciriaco, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Bella, Noemi La, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lu, Ru-Sen, Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moscibrodzka, Monika, Müller, Cornelia, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yamaguchi, Paul, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, Zhang, Shuo, Zhao, Shan-Shan, Broderick, Avery E., Gold, Roman, Georgiev, Boris, Pesce, Dominic W., Tiede, Paul, Ni, Chunchong, Moriyama, Kotaro, Akiyama, Kazunori, Alberdi, Antxon, Alef, Walter, Algaba, Juan Carlos, Anantua, Richard, Asada, Keiichi, Azulay, Rebecca, Bach, Uwe, Baczko, Anne-Kathrin, Ball, David, Baloković, Mislav, Barrett, John, Bauböck, Michi, Benson, Bradford A., Bintley, Dan, Blackburn, Lindy, Blundell, Raymond, Bouman, Katherine L., Bower, Geoffrey C., Boyce, Hope, Bremer, Michael, Brinkerink, Christiaan D., Brissenden, Roger, Britzen, Silke, Broguiere, Dominique, Bronzwaer, Thomas, Bustamante, Sandra, Byun, Do-Young, Carlstrom, John E., Ceccobello, Chiara, Chael, Andrew, Chan, Chi-kwan, Chatterjee, Koushik, Chatterjee, Shami, Chen, Ming-Tang, Chen, Yongjun, Cheng, Xiaopeng, Cho, Ilje, Christian, Pierre, Conroy, Nicholas S., Conway, John E., Cordes, James M., Crawford, Thomas M., Crew, Geoffrey B., Cruz-Osorio, Alejandro, Cui, Yuzhu, Davelaar, Jordy, De Laurentis, Mariafelicia, Deane, Roger, Dempsey, Jessica, Desvignes, Gregory, Dexter, Jason, Dhruv, Vedant, Doeleman, Sheperd S., Dougal, Sean, Dzib, Sergio A., Eatough, Ralph P., Emami, Razieh, Falcke, Heino, Farah, Joseph, Fish, Vincent L., Fomalont, Ed, Ford, H. Alyson, Fraga-Encinas, Raquel, Freeman, William T., Friberg, Per, Fromm, Christian M., Fuentes, Antonio, Galison, Peter, Gammie, Charles F., García, Roberto, Gentaz, Olivier, Goddi, Ciriaco, Gómez-Ruiz, Arturo I., Gómez, José L., Gu, Minfeng, Gurwell, Mark, Hada, Kazuhiro, Haggard, Daryl, Haworth, Kari, Hecht, Michael H., Hesper, Ronald, Heumann, Dirk, Ho, Luis C., Ho, Paul, Honma, Mareki, Huang, Chih-Wei L., Huang, Lei, Hughes, David H., Ikeda, Shiro, Impellizzeri, C. M. Violette, Inoue, Makoto, Issaoun, Sara, James, David J., Jannuzi, Buell T., Janssen, Michael, Jeter, Britton, Jiang, Wu, Jiménez-Rosales, Alejandra, Johnson, Michael D., Jorstad, Svetlana, Joshi, Abhishek V., Jung, Taehyun, Karami, Mansour, Karuppusamy, Ramesh, Kawashima, Tomohisa, Keating, Garrett K., Kettenis, Mark, Kim, Dong-Jin, Kim, Jae-Young, Kim, Jongsoo, Kim, Junhan, Kino, Motoki, Koay, Jun Yi, Kocherlakota, Prashant, Kofuji, Yutaro, Koch, Patrick M., Koyama, Shoko, Kramer, Carsten, Kramer, Michael, Krichbaum, Thomas P., Kuo, Cheng-Yu, Bella, Noemi La, Lauer, Tod R., Lee, Daeyoung, Lee, Sang-Sung, Leung, Po Kin, Levis, Aviad, Li, Zhiyuan, Lico, Rocco, Lindahl, Greg, Lindqvist, Michael, Lisakov, Mikhail, Liu, Jun, Liu, Kuo, Liuzzo, Elisabetta, Lo, Wen-Ping, Lobanov, Andrei P., Loinard, Laurent, Lonsdale, Colin J., Lu, Ru-Sen, Mao, Jirong, Marchili, Nicola, Markoff, Sera, Marrone, Daniel P., Marscher, Alan P., Martí-Vidal, Iván, Matsushita, Satoki, Matthews, Lynn D., Menten, Karl M., Michalik, Daniel, Mizuno, Izumi, Mizuno, Yosuke, Moran, James M., Moscibrodzka, Monika, Müller, Cornelia, Mus, Alejandro, Musoke, Gibwa, Myserlis, Ioannis, Nadolski, Andrew, Nagai, Hiroshi, Nagar, Neil M., Nakamura, Masanori, Narayan, Ramesh, Narayanan, Gopal, Natarajan, Iniyan, Nathanail, Antonios, Fuentes, Santiago Navarro, Neilsen, Joey, Neri, Roberto, Noutsos, Aristeidis, Nowak, Michael A., Oh, Junghwan, Okino, Hiroki, Olivares, Héctor, Ortiz-León, Gisela N., Oyama, Tomoaki, Palumbo, Daniel C. M., Paraschos, Georgios Filippos, Park, Jongho, Parsons, Harriet, Patel, Nimesh, Pen, Ue-Li, Piétu, Vincent, Plambeck, Richard, PopStefanija, Aleksandar, Porth, Oliver, Pötzl, Felix M., Prather, Ben, Preciado-López, Jorge A., Pu, Hung-Yi, Ramakrishnan, Venkatessh, Rao, Ramprasad, Rawlings, Mark G., Raymond, Alexander W., Rezzolla, Luciano, Ricarte, Angelo, Ripperda, Bart, Roelofs, Freek, Rogers, Alan, Ros, Eduardo, Romero-Cañizales, Cristina, Roshanineshat, Arash, Rottmann, Helge, Roy, Alan L., Ruiz, Ignacio, Ruszczyk, Chet, Rygl, Kazi L. J., Sánchez, Salvador, Sánchez-Argüelles, David, Sánchez-Portal, Miguel, Sasada, Mahito, Satapathy, Kaushik, Savolainen, Tuomas, Schloerb, F. Peter, Schonfeld, Jonathan, Schuster, Karl-Friedrich, Shao, Lijing, Shen, Zhiqiang, Small, Des, Sohn, Bong Won, SooHoo, Jason, Souccar, Kamal, Sun, He, Tazaki, Fumie, Tetarenko, Alexandra J., Tilanus, Remo P. J., Titus, Michael, Torne, Pablo, Traianou, Efthalia, Trent, Tyler, Trippe, Sascha, Turk, Matthew, van Bemmel, Ilse, van Langevelde, Huib Jan, van Rossum, Daniel R., Vos, Jesse, Wagner, Jan, Ward-Thompson, Derek, Wardle, John, Weintroub, Jonathan, Wex, Norbert, Wharton, Robert, Wielgus, Maciek, Wiik, Kaj, Witzel, Gunther, Wondrak, Michael F., Wong, George N., Wu, Qingwen, Yamaguchi, Paul, Yoon, Doosoo, Young, André, Young, Ken, Younsi, Ziri, Yuan, Feng, Yuan, Ye-Fei, Zensus, J. Anton, Zhao, Guang-Yao, Zhang, Shuo, and Zhao, Shan-Shan
Abstract: The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.
Published: 2022

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