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1. A Two-Week $IXPE$ Monitoring Campaign on Mrk 421

Author: Maksym, W. Peter, Liodakis, Ioannis, Saade, M. Lynne, Kim, Dawoon E., Middei, Riccardo, Di Gesu, Laura, Kiehlmann, Sebastian, Matzeu, Gabriele, Agudo, Iván, Marscher, Alan P., Ehlert, Steven R., Jorstad, Svetlana G., Kaaret, Philip, Marshall, Herman L., Pacciani, Luigi, Perri, Matteo, Puccetti, Simonetta, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Morcuende, Daniel, Otero-Santos, Jorge, Sota, Alfredo, Piirola, Vilppu, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, McCall, Callum, Jermak, Helen E., Steele, Iain A., Borman, George A., Grishina, Tatiana S., Hagen-Thorn, Vladimir A., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Shishkina, Ekaterina V., Troitskiy, Ivan S., Troitskaya, Yulia V., Vasilyev, Andrey A., Zhovtan, Alexey V., Myserlis, Ioannis, Gurwell, Mark, Keating, Garrett, Rao, Ramprasad, Pauley, Colt, Angelakis, Emmanouil, Kraus, Alexander, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Poutanen, Juri, Sakanoi, Takeshi, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Song, Chanwoo, Blinov, Dmitry, Shablovinskaya, Elena, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccoló, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the first dense X-ray polarization monitoring campaign on the blazar Mrk 421. Our observations were accompanied by an even denser radio and optical polarization campaign. We find significant short-timescale variability in both X-ray polarization degree and angle, including a $\sim90^\circ$ angle rotation about the jet axis. We attribute this to random variations of the magnetic field, consistent with the presence of turbulence but also unlikely to be explained by turbulence alone. At the same time, the degree of lower-energy polarization is significantly lower and shows no more than mild variability. Our campaign provides further evidence for a scenario in which energy-stratified shock-acceleration of relativistic electrons, combined with a turbulent magnetic field, is responsible for optical to X-ray synchrotron emission in blazar jets., Comment: 23 pages, including 8 pages of appendices. 12 figures, 3 tables. Submitted to ApJ
Published: 2024

2. 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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3. Probing the high frequency variability of NGC 5044: the key to AGN feedback

Author: Schellenberger, Gerrit, O'Sullivan, Ewan, David, Laurence, Vrtilek, Jan, Romero, Charles, Petitpas, Glen, Forman, William, Giacintucci, Simona, Gurwell, Mark, Jones, Christine, Rajpurohit, Kamlesh, Ubertosi, Francesco, and Venturi, Tiziana
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The active galactic nucleus (AGN) feeding and feedback process in the centers of galaxy clusters and groups is still not well understood. NGC 5044 is the ideal system in which to study AGN feedback. It hosts the largest known reservoir of cold gas in any cool-core galaxy group, and features several past epochs of AGN feedback imprinted as cavities in the X-ray bright intragroup medium (IGrM), as well as parsec scale jets. We present Submillimeter Array (SMA), Karl G. Jansky Very Large Array (VLA), James Clerk Maxwell Telescope (JCMT), and Atacama Large Millimeter/submillimeter Array (ALMA) high frequency observations of NGC 5044 to assess the time variability of the mmwaveband emission from the accretion disk, and quantify the Spectral Energy Distribution (SED) from the radio to sub-millimeter band. The SED is well described by advection dominated accretion flow (ADAF) model and self-absorbed jet emission from an aging plasma with tau = 1kyr. We find a characteristic variability timescale of 150 days, which constrains the ADAF emission region to about 0.1pc, and the magnetic field to 4.7mG in the jets and and 870G in the accretion disk. A longer monitoring/sampling will allow to understand if the underlying process is truly periodic in nature., Comment: 17 pages, 7 figures, accepted for publication in ApJ
Published: 2024

4. X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023

Author: Chen, Chien-Ting J., Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Di Gesu, Laura, Di Marco, Alessandro, Ehlert, Steven R., Errando, Manel, Negro, Michela, Jorstad, Svetlana G., Marscher, Alan P., Wu, Kinwah, Agudo, Iván, Poutanen, Juri, Mizuno, Tsunefumi, Kouch, Pouya M., Lindfors, Elina, Borman, George A., Grishina, Tatiana S., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Troitsky, Ivan S., Troitskaya, Yulia V., Vasilyev, Andrey A., Zhovtan, Alexey V., Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Santos, Jorge Otero, Sota, Alfredo, Piirola, Vilppu, Myserlis, Ioannis, Angelakis, Emmanouil, Kraus, Alexander, Gurwell, Mark, Keating, Garrett, Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Song, Chanwoo, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Nitindala, Anagha P., Sakanoi, Takeshi, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Nakaoka, Tatsuya, Akitaya, Hiroshi, Casadio, Carolina, Sievers, Albrecht, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccoló, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Polarimetry Explorer (IXPE) with six 100-ks observations spanning from 2022 March to 2023 April. Each IXPE observation was accompanied by simultaneous X-ray data from NuSTAR, Swift/XRT, and/or XMM-Newton. Complementary optical-infrared polarization measurements were also available in the B, V, R, I, and J bands, as were radio polarization measurements from 4.85 GHz to 225.5 GHz. Among the first five IXPE observations, we did not find significant variability in the X-ray polarization degree and angle with IXPE. However, the most recent sixth observation found an elevated polarization degree at $>3\sigma$ above the average of the other five observations. The optical and radio measurements show no apparent correlations with the X-ray polarization properties. Throughout the six IXPE observations, the X-ray polarization degree remained higher than, or similar to, the R-band optical polarization degree, which remained higher than the radio value. This is consistent with the energy-stratified shock scenario proposed to explain the first two IXPE observations, in which the polarized X-ray, optical, and radio emission arises from different regions., Comment: Accepted for publication in ApJ
Published: 2024

5. Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654

Author: Meyer, Eileen T., Laha, Sibasish, Shuvo, Onic I., Roychowdhury, Agniva, Green, David A., Rhodes, Lauren, Hankla, Amelia M., Philippov, Alexander, Mbarek, Rostom, laor, Ari, Begelman, Mitchell C., Sadaula, Dev R., Ghosh, Ritesh, Bruni, Gabriele, Panessa, Francesca, Guainazzi, Matteo, Behar, Ehud, Masterson, Megan, Zhang, Haocheng, Yang, Xiaolong, Gurwell, Mark A., Keating, Garrett K., Williams-Baldwin, David, Bray, Justin D., Bempong-Manful, Emmanuel K., Wrigley, Nicholas, Bianchi, Stefano, Ricci, Federica, La Franca, Fabio, Kara, Erin, Georganopoulos, Markos, Oates, Samantha, Nicholl, Matt, Pal, Main, and Cenko, S. Bradley
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN after an optical outburst in late 2017 and has since displayed considerable changes in X-ray emission, including the destruction and rebuilding of the X-ray corona in 2019-2020. Radio observations prior to 2023 show a faint and compact radio source typical of radio-quiet AGN. Starting in February 2023, 1ES 1927+654 began exhibiting a radio flare with a steep exponential rise, reaching a peak 60 times previous flux levels, and has maintained this higher level of radio emission for over a year to date. The 5-23 GHz spectrum is broadly similar to gigahertz-peaked radio sources, which are understood to be young radio jets less than ~1000 years old. Recent high-resolution VLBA observations at 23.5 GHz now show resolved extensions on either side of the core, with a separation of ~0.15 pc, consistent with a new and mildly relativistic bipolar outflow. A steady increase in the soft X-ray band (0.3-2 keV) concurrent with the radio may be consistent with jet-driven shocked gas, though further observations are needed to test alternate scenarios. This source joins a growing number of CL-AGN and tidal disruption events which show late-time radio activity, years after the initial outburst., Comment: Submitted to ApJ Letters 24 June 2024; Accepted 14 October 2024
Published: 2024

6. Upgrading the Submillimeter Array: wSMA and beyond

Author: Grimes, Paul K., Keating, Garrett K., Blundell, Raymond, Christensen, Robert D., Gurwell, Mark, Kovacs, Attila, Norton, Timothy, Paine, Scott N., Rao, Ramprasad, Tong, Edward C. -Y., Weintroub, Jonathan, Wilner, David, Wilson, Robert W., Zeng, Lingzhen, and Zhang, Qizhou
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Submillimeter Array (SMA) is an array of 8 antennas operating at millimeter and submillimeter wavelengths on Maunakea, Hawaii, operated by the Smithsonian Astrophysical Observatory and Academia Sinica Institute of Astronomy and Astrophysics, Taiwan. Over the past several years, we have been preparing a major upgrade to the SMA that will replace the aging original receiver cryostats and receiver cartridges with all new cryostats and new 230 and 345 GHz receiver designs. This wideband upgrade (wSMA) will also include significantly increased instantaneous bandwidth, improved sensitivity, and greater capabilities for dual frequency observations. In this paper, we will describe the wSMA receiver upgrade and status, as well as the future upgrades that will be enabled by the deployment of the wSMA receivers., Comment: To be published in the proceedings of SPIE Astronomical Telescopes + Instrumentation 2024, paper number 13096-122
Published: 2024

7. IXPE observation of PKS 2155-304 reveals the most highly polarized blazar

Author: Kouch, Pouya M., Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Tavecchio, Fabrizio, Marscher, Alan P., Marshall, Herman L., Ehlert, Steven R., Di Gesu, Laura, Jorstad, Svetlana G., Agudo, Iván, Madejski, Grzegorz M., Romani, Roger W., Errando, Manel, Lindfors, Elina, Nilsson, Kari, Toppari, Ella, Potter, Stephen B., Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, McCall, Callum, Jermak, Helen E., Steele, Iain A., Myserlis, Ioannis, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Angelakis, Emmanouil, Kraus, Alexander, Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Escudero, Juan, Agís-González, Beatriz, Husillos, César, Morcuende, Daniel, Otero-Santos, Jorge, Sota, Alfredo, Bachev, Rumen, Antonelli, Lucio Angelo, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel Lawrence, Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the X-ray polarization properties of the high-synchrotron-peaked (HSP) blazar PKS 2155$-$304 based on observations with the Imaging X-ray Polarimetry Explorer (IXPE). We observed the source between Oct 27 and Nov 7, 2023. We also conducted an extensive contemporaneous multiwavelength (MW) campaign. We find that during the first half ($T_1$) of the IXPE pointing, the source exhibited the highest X-ray polarization degree detected for an HSP blazar thus far, (30.7$\pm$2.0)%, which dropped to (15.3$\pm$2.1)% during the second half ($T_2$). The X-ray polarization angle remained stable during the IXPE pointing at 129.4$^\circ$$\pm$1.8$^\circ$ and 125.4$^\circ$$\pm$3.9$^\circ$ during $T_1$ and $T_2$, respectively. Meanwhile, the optical polarization degree remained stable during the IXPE pointing, with average host-galaxy-corrected values of (4.3$\pm$0.7)% and (3.8$\pm$0.9)% during the $T_1$ and $T_2$, respectively. During the IXPE pointing, the optical polarization angle changed achromatically from $\sim$140$^\circ$ to $\sim$90$^\circ$ and back to $\sim$130$^\circ$. Despite several attempts, we only detected (99.7% conf.) the radio polarization once (during $T_2$, at 225.5 GHz): with degree (1.7$\pm$0.4)% and angle 112.5$^\circ$$\pm$5.5$^\circ$. The direction of the broad pc-scale jet is rather ambiguous and has been found to point to the east and south at different epochs; however, on larger scales (> 1.5 pc) the jet points toward the southeast ($\sim$135$^\circ$), similar to all of the MW polarization angles. Moreover, the X-ray to optical polarization degree ratios of $\sim$7 and $\sim$4 during $T_1$ and $T_2$, respectively, are similar to previous IXPE results for several HSP blazars. These findings, combined with the lack of correlation of temporal variability between the MW polarization properties, agree with an energy-stratified shock-acceleration scenario in HSP blazars., Comment: 17 pages, 10 figures, 4 tables, Accepted for publication in A&A
Published: 2024
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8. SMA 200-400 GHz Survey for Dust Properties in the Icy Class II Disks in the Taurus Molecular Cloud

Author: Chung, Chia-Ying, Andrews, Sean M., Gurwell, Mark A., Wright, Melvyn, Long, Feng, Xu, Wenrui, and Liu, Hauyu Baobab
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: We present a new SMA survey of 47 Class II sources in the Taurus-Auriga region. Our observations made 12 independent samples of flux densities over the 200-400 GHz frequency range. We tightly constrained the spectral indices of most sources to a narrow range of $2.0\pm0.2$; only a handful of spatially resolved (e.g., diameter $>$250 au) disks present larger spectral indices. The simplest interpretation for this result is that the (sub)millimeter luminosities of all of the observed target sources are dominated by very optically thick (e.g., $\tau\gtrsim$5) dust thermal emission. Some previous works that were based on the optically thin assumption thus might have underestimated optical depths by at least one order of magnitude. Assuming DSHARP dust opacities, this corresponds to underestimates of dust masses by a similar factor. Moreover, some population synthesis models show that to explain the observed, narrowly distributed spectral indices, the disks in our selected sample need to have very similar dust temperatures ($T_{\small{dust}}$). Given a specific assumption of median $T_{\small{dust}}$, the maximum grain sizes ($a_{\small{max}}$) can also be constrained, which is a few times smaller than 0.1 mm for $T_{\small{dust}}\sim$100 K and a few mm for $T_{\small{dust}}\sim$24 K. The results may indicate that dust grain growth outside the water snowline is limited by the bouncing/fragmentation barriers. In the Class II disks, the dust mass budget outside of the water snowline may be largely retained instead of being mostly consumed by planet formation. While Class II disks still possess sufficient dust masses to feed planet formation at a later time, it is unknown whether or not dust coagulation and planet formation can be efficient or natural outside of the water snowline., Comment: accepted by Astrophysical Journal Supplement
Published: 2024

9. The flaring activity of blazar AO 0235+164 during year 2021

Author: Pedrosa, Juan Escudero, Agudo, Iván, Moritz, Till, Marscher, Alan P., Jorstad, Svetlana, Tramacere, Andrea, Casadio, Carolina, Thum, Clemens, Myserlis, Ioannis, Sievers, Albrecht, Otero-Santos, Jorge, Morcuende, Daniel, López-Coto, Rubén, D'Ammando, Filippo, Bonnoli, Giacomo, Gurwell, Mark, Gómez, José Luis, Rao, Ramprasad, and Keating, Garrett
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. The blazar AO 0235+164, located at redshift $z=0.94$, has displayed interesting and repeating flaring activity in the past, the latest episodes occurring in 2008 and 2015. In 2020, the source brightened again, starting a new flaring episode that peaked in 2021. Aims. We study the origin and properties of the 2021 flare in relation to previous studies and the historical behavior of the source, in particular to the 2008 and 2015 flaring episodes. Methods. We analyze the multi-wavelength photo-polarimetric evolution of the source. From Very Long Baseline Array images, we derive the kinematic parameters of new components associated with the 2021 flare. We use this information to constrain a model for the spectral energy distribution of the emission during the flaring period. We propose an analytical geometric model to test whether the observed wobbling of the jet is consistent with precession. Results. We report the appearance of two new components that are ejected in a different direction than previously, confirming the wobbling of the jet. We find that the direction of ejection is consistent with that of a precessing jet.The derived period independently agrees with the values commonly found in the literature. Modeling of the spectral energy distribution further confirm that the differences between flares can be attributed to geometrical effects., Comment: Accepted 15 May 2024
Published: 2024
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10. Observations of Titan's Stratosphere During Northern Summer: Temperatures, CH3CN and CH3D Abundances

Author: Thelen, Alexander E., Nixon, Conor A., Cordiner, Martin A., Lellouch, Emmanuel, Vinatier, Sandrine, Teanby, Nicholas A., Butler, Bryan, Charnley, Steven B., Cosentino, Richard G., de Kleer, Katherine, Irwin, Patrick G. J., Gurwell, Mark A., Kisiel, Zbigniew, and Moreno, Raphael
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: Titan's atmospheric composition and dynamical state have previously been studied over numerous epochs by both ground- and space-based facilities. However, stratospheric measurements remain sparse during Titan's northern summer and fall. The lack of seasonal symmetry in observations of Titan's temperature field and chemical abundances raises questions about the nature of the middle atmosphere's meridional circulation and evolution over Titan's 29-yr seasonal cycle that can only be answered through long-term monitoring campaigns. Here, we present maps of Titan's stratospheric temperature, acetonitrile (or methyl cyanide; CH$_3$CN), and monodeuterated methane (CH$_3$D) abundances following Titan's northern summer solstice obtained with Band 9 ($\sim0.43$ mm) ALMA observations. We find that increasing temperatures towards high-southern latitudes, currently in winter, resemble those observed during Titan's northern winter by the Cassini mission. Acetonitrile abundances have changed significantly since previous (sub)millimeter observations, and we find that the species is now highly concentrated at high-southern latitudes. The stratospheric CH$_3$D content is found to range between 4-8 ppm in these observations, and we infer the CH$_4$ abundance to vary between $\sim0.9-1.6\%$ through conversion with previously measured D/H values. A global value of CH$_4=1.15\%$ was retrieved, lending further evidence to the temporal and spatial variability of Titan's stratospheric methane when compared with previous measurements. Additional observations are required to determine the cause and magnitude of stratospheric enhancements in methane during these poorly understood seasons on Titan., Comment: Accepted for publication in the Planetary Science Journal. 9 Figures, 1 table
Published: 2024

11. Measurements of Titan's Stratospheric Winds during the 2009 Equinox with the eSMA

Author: Light, Siobhan, Gurwell, Mark, Thelen, Alexander, Lombardo, Nicholas, and Nixon, Conor
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: Saturn's moon Titan possesses stratospheric zonal winds that places it among a sparse class of planetary bodies known to have superrotation in their atmospheres. Few measurements have been made of these speeds in the upper stratosphere, leaving their seasonal variations still not well understood. We examined observations made with the extended Submillimeter Array (eSMA) in 2009 March (L\textsubscript{s}=355\textdegree{}) and 2010 February (L\textsubscript{s}=5\textdegree{}), shortly before and after Titan's northern spring equinox. Cassini observations and atmospheric models find equinoctial periods to be especially dynamic. Zonal wind calculations, derived from the Doppler frequency shift of CH\textsubscript{3}CN near 349.4 GHz, yielded speeds of 128 $\pm$ 27 m s\textsuperscript{-1} in 2009 and 209 $\pm$ 48 m s\textsuperscript{-1} in 2010. We estimated the measured emission to originate from vertical altitudes of $336^{+112}_{-88}$ kilometers, equivalent to pressures of $3.8^{+19.2}_{-3.4}$ Pa, commensurate with Titan's upper stratosphere/lower mesosphere. This suggests a possible increase in zonal speeds during this period. The results are then compared to those from previous Cassini-inferred and direct-interferometric observations of winds, as well as general circulation model simulations, to form a more complete picture of the seasonal cycle of stratospheric zonal winds., Comment: Accepted to the Planetary Science Journal; will be published 2024 April 12
Published: 2024
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12. Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Planetary and Cometary Atmospheres

Author: Cordiner, Martin A., Thelen, Alexander E., Cavalié, Thibault, Cosentino, Richard, Fletcher, Leigh N., Gurwell, Mark, de Kleer, Katherine, Kuan, Yi-Jehng, Lellouch, Emmanuel, Moullet, Arielle, Nixon, Conor, de Pater, Imke, Teanby, Nicholas A., Butler, Bryan, Charnley, Steven, Moreno, Raphael, Booth, Mark, Klaassen, Pamela, Cicone, Claudia, Mroczkowski, Tony, Di Mascolo, Luca, Johnstone, Doug, van Kampen, Eelco, Lee, Minju M., Liu, Daizhong, Maccarone, Thomas J., Saintonge, Amélie, Smith, Matthew, and Wedemeyer, Sven
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The study of planets and small bodies within our Solar System is fundamental for understanding the formation and evolution the Earth and other planets. Compositional and meteorological studies of the giant planets provide a foundation for understanding the nature of the most commonly observed exoplanets, while spectroscopic observations of the atmospheres of terrestrial planets, moons, and comets provide insights into the past and present-day habitability of planetary environments, and the availability of the chemical ingredients for life. While prior and existing (sub)millimeter observations have led to major advances in these areas, progress is hindered by limitations in the dynamic range, spatial and temporal coverage, as well as sensitivity of existing telescopes and interferometers. Here, we summarize some of the key planetary science use cases that factor into the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m class single dish facility: (1) to more fully characterize planetary wind fields and atmospheric thermal structures, (2) to measure the compositions of icy moon atmospheres and plumes, (3) to obtain detections of new, astrobiologically relevant gases and perform isotopic surveys of comets, and (4) to perform synergistic, temporally-resolved measurements in support of dedicated interplanetary space missions. The improved spatial coverage (several arcminutes), resolution ($\sim1.2''-12''$), bandwidth (several tens of GHz), dynamic range ($\sim10^5$) and sensitivity ($\sim1$ mK km s$^{-1}$) required by these science cases would enable new insights into the chemistry and physics of planetary environments, the origins of prebiotic molecules and the habitability of planetary systems in general., Comment: Submitted to Open Research Europe (AtLAST collection). 19 pages
Published: 2024

13. Detection of X-ray Polarization from the Blazar 1ES 1959+650 with the Imaging X-ray Polarimetry Explorer

Author: Errando, Manel, Liodakis, Ioannis, Marscher, Alan P., Marshall, Herman L., Middei, Riccardo, Negro, Michela, Peirson, Abel Lawrence, Perri, Matteo, Puccetti, Simonetta, Rabinowitz, Pazit L., Agudo, Iván, Jorstad, Svetlana G., Savchenko, Sergey S., Blinov, Dmitry, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Aceituno, Francisco José, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Víctor, Agís-González, Beatriz, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Kouch, Pouya M., Lindfors, Elina, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Ingram, Adam, Massaro, Francesco, Antonelli, Lucio Angelo, Bonino, Raffaella, Cavazzuti, Elisabetta, Chen, Chien-Ting, Cibrario, Nicolò, Ciprini, Stefano, De Rosa, Alessandra, Di Gesu, Laura, Di Pierro, Federico, Donnarumma, Immacolata, Ehlert, Steven R., Fenu, Francesco, Gau, Ephraim, Karas, Vladimir, Kim, Dawoon E., Krawczynski, Henric, Laurenti, Marco, Lisalda, Lindsey, López-Coto, Rubén, Madejski, Grzegorz, Marin, Frédéric, Marinucci, Andrea, Mitsuishi, Ikuyuki, Muleri, Fabio, Pacciani, Luigi, Paggi, Alessandro, Petrucci, Pierre-Olivier, Cavero, Nicole Rodriguez, Romani, Roger W., Tavecchio, Fabrizio, Tugliani, Stefano, Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Matt, Giorgio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Observations of linear polarization in the 2-8 keV energy range with the Imaging X-ray Polarimetry Explorer (IXPE) explore the magnetic field geometry and dynamics of the regions generating non-thermal radiation in relativistic jets of blazars. These jets, particularly in blazars whose spectral energy distribution peaks at X-ray energies, emit X-rays via synchrotron radiation from high-energy particles within the jet. IXPE observations of the X-ray selected BL Lac-type blazar 1ES 1959+650 in 2022 May 3-4 showed a significant linear polarization degree of $\Pi_\mathrm{x} = 8.0\% \pm 2.3\%$ at an electric-vector position angle $\psi_\mathrm{x} = 123^\circ \pm 8^\circ$. However, in 2022 June 9-12, only an upper limit of $\Pi_\mathrm{x} \leq 5.1\%$ could be derived (at the 99% confidence level). The degree of optical polarization at that time $\Pi_\mathrm{O} \sim 5\%$ is comparable to the X-ray measurement. We investigate possible scenarios for these findings, including temporal and geometrical depolarization effects. Unlike some other X-ray selected BL Lac objects, there is no significant chromatic dependence of the measured polarization in 1ES 1959+650, and its low X-ray polarization may be attributed to turbulence in the jet flow with dynamical timescales shorter than 1 day., Comment: 16 pages, 4 figures, accepted for publication in The Astrophysical Journal
Published: 2024
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14. On the Origin of the X-ray Emission in Heavily Obscured Compact Radio Sources

Author: Król, Dominika Ł., Sobolewska, Małgosia, Stawarz, Łukasz, Siemiginowska, Aneta, Migliori, Giulia, Principe, Giacomo, and Gurwell, Mark A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: X-ray continuum emission of active galactic nuclei (AGNs) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. Here we discuss the broad-band emission of three radio-loud AGN belonging to the class of compact symmetric objects (CSOs), with detected narrow Fe\,K$\alpha$ lines. CSOs have newly-born radio jets, forming compact radio lobes with projected linear sizes of the order of a few to hundreds of parsecs. We model the radio--to--$\gamma$-ray spectra of compact lobes in {J1407+2827}, J1511+0518, and {J2022+6137}, which are among the nearest and the youngest CSOs known to date, and are characterized by an intrinsic X-ray absorbing column density of $N_{\rm H} > 10^{23}$\,cm$^{-2}$. In addition to the archival data, we analyze the newly acquired \chandra\ X-ray Observatory and Sub-Millimeter Array (SMA) observations, and also refine the $\gamma$-ray upper limits from the \fermi\ Large Area Telescope (LAT) monitoring. The new \chandra\ data exclude the presence of the extended X-ray emission components on scales larger than $1.5^{\prime \prime}$. The SMA data unveil a correlation of the spectral index of the electron distribution in the lobes and $N_{\rm H}$, which can explain the $\gamma$-ray quietness of heavily obscured CSOs. Based on our modeling, we argue that the inverse-Compton emission of compact radio lobes may account for the intrinsic X-ray continuum in all these sources. Furthermore, we propose that the observed iron lines may be produced by a reflection of the lobes' continuum from the surrounding cold dust., Comment: The Astrophysical Journal, in press
Published: 2023

15. X-ray detection of the most extreme star-forming galaxies at the cosmic noon via strong lensing

Author: Wang, Q. Daniel, Diaz, Carlos Garcia, Kamieneski, Patrick S., Harrington, Kevin C., Yun, Min S., Foo, Nicholas, Frye, Brenda L., Jimenez-Andrade, Eric F., Liu, Daizhong, Lowenthal, James D., Pampliega, Belen Alcalde, Pascale, Massimo, Vishwas, Amit, and Gurwell, Mark A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: Hyper-luminous infrared galaxies (HyLIRGs) are the most extreme star-forming systems observed in the early Universe, and their properties still elude comprehensive understanding. We have undertaken a large XMM-Newton observing program to probe the total accreting black hole population in three HyLIRGs at z = 2.12, 3.25, and 3.55, gravitationally lensed by foreground galaxies. Selected from the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts (PASSAGES), these HyLIRGs have apparent infrared luminosities > E14 Lsun. Our observations revealed X-ray emission in each of them. PJ1336+49 appears to be dominated by high-mass X-ray binaries (HMXBs). Remarkably, the luminosity of this non-AGN X-ray emission exceeds by a factor of about three the value obtained by calibration with local galaxies with much lower star formation rates. This enhanced X-ray emission most likely highlights the efficacy of dynamical HMXB production within compact clusters, which is an important mode of star formation in HyLIRGs. The remaining two (PJ0116-24 and PJ1053+60) morphologically and spectrally exhibit a compact X-ray component in addition to the extended non-AGN X-ray emission, indicating the presence of Active Galactic Nuclei (AGNs). The AGN appears to be centrally located in the reconstructed source plane images of PJ0116-24, which manifests its star-forming activity predominantly within an extended galactic disk. In contrast, the AGN in the field of PJ1053+60 is projected 60 kpc away from the extreme star-forming galaxy and could be ejected from it. These results underline the synergistic potential of deep X-ray observations with strong lensing for the study of high-energy astrophysical phenomena in HyLIRGs., Comment: Just accepted for publication in MNRAS; comments are welcome
Published: 2023

16. Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE

Author: Veledina, Alexandra, Muleri, Fabio, Poutanen, Juri, Podgorný, Jakub, Dovčiak, Michal, Capitanio, Fiamma, Churazov, Eugene, De Rosa, Alessandra, Di Marco, Alessandro, Forsblom, Sofia V., Kaaret, Philip, Krawczynski, Henric, La Monaca, Fabio, Loktev, Vladislav, Lutovinov, Alexander A., Molkov, Sergey V., Mushtukov, Alexander A., Ratheesh, Ajay, Rodriguez Cavero, Nicole, Steiner, James F., Sunyaev, Rashid A., Tsygankov, Sergey S., Weisskopf, Martin C., Zdziarski, Andrzej A., Bianchi, Stefano, Bright, Joe S., Bursov, Nikolaj, Costa, Enrico, Egron, Elise, Garcia, Javier A., Green, David A., Gurwell, Mark, Ingram, Adam, Kajava, Jari J. E., Kale, Ruta, Kraus, Alex, Malyshev, Denys, Marin, Frédéric, Matt, Giorgio, McCollough, Michael, Mereminskiy, Ilya A., Nizhelsky, Nikolaj, Piano, Giovanni, Pilia, Maura, Pittori, Carlotta, Rao, Ramprasad, Righini, Simona, Soffitta, Paolo, Shevchenko, Anton, Svoboda, Jiri, Tombesi, Francesco, Trushkin, Sergei A., Tsybulev, Peter, Ursini, Francesco, Wu, Kinwah, Agudo, Iván, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Donnarumma, Immacolata, Doroshenko, Victor, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Negro, Michela, Ng, Chi-Yung, O’Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Roberts, Oliver, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Swartz, Doug, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Trois, Alessio, Turolla, Roberto, Vink, Jacco, Xie, Fei, and Zane, Silvia
Published: 2024
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17. A Near Magnetic-to-kinetic Energy Equipartition Flare from the Relativistic Jet in AO 0235+164 during 2013-2019

Author: Cheong, Whee Yeon, Lee, Sang-Sung, Kim, Sang-Hyun, Kang, Sincheol, Kim, Jae Young, Rani, Bindu, Readhead, Anthony C. S., Kiehlmann, Sebastian, Lähteenmäki, Anne, Tornikoski, Merja, Tammi, Joni, Ramakrishnan, Venkatessh, Agudo, Iván, Fuentes, Antonio, Traianou, Efthalia, Escudero, Juan, Thum, Clemens, Myserlis, Ioannis, Casadio, Carolina, and Gurwell, Mark
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the multiwavelength flaring activity of the blazar AO 0235+164 during its recent active period from 2013 to 2019. From a discrete correlation function (DCF) analysis, we find a significant (>95%) correlation between radio and $\gamma$-ray light curves with flares at longer wavelengths following flares at shorter wavelengths. We identify a new jet component in 43 GHz VLBA data that was ejected from the radio core on MJD $57246^{+26}_{-30}$ (2015 August 12), during the peak of the 2015 radio flare. From the analysis of the jet component, we derived a Doppler factor of $\delta_{\rm var}=28.5\pm8.4$, a bulk Lorentz factor of $\Gamma=16.8^{+3.6}_{-3.1}$, and an intrinsic viewing angle of $\theta_{\rm v}=1.42^{+1.07}_{-0.52}\textrm{ degrees}$. Investigation of the quasi-simultaneous radio data revealed a partially absorbed spectrum with the turnover frequency varying in the range of $10-70$ GHz and the peak flux density varying in the range of $0.7-4$ Jy. We find the synchrotron self-absorption magnetic field strength to be $B_{\rm SSA}=15.3^{+12.6}_{-14.0}$ mG at the peak of the 2015 radio flare, which is comparable to the equipartition magnetic field strength of $B_{\rm EQ}=43.6^{+10.6}_{-10.4}$ mG calculated for the same epoch. Additional analysis of the radio emission region in the relativistic jet of AO 0235+164 suggests that it did not significantly deviate from equipartition during its recent flaring activity., Comment: 13 pages, 11 figures, 4 tables; Accepted for publication in MNRAS
Published: 2023

18. Magnetic Field Properties inside the Jet of Mrk 421: Multiwavelength Polarimetry Including the Imaging X-ray Polarimetry Explorer

Author: Kim, Dawoon E., Di Gesu, Laura, Liodakis, Ioannis, Marscher, Alan P., Jorstad, Svetlana G., Midde, Riccardo, Marshall, Herman L., Pacciani, Luigi, Agudo, Iván, Tavecchio, Fabrizio, Cibrario, Nicolò, Tugliani, Stefano, Bonino, Raffaella, Negro, Michela, Puccetti, Simonetta, Tombesi, Francesco, Costa, Enrico, Donnarumma, Immacolata, Soffitta, Paolo, Mizuno, Tsunefumi, Fukazawa, Yasushi, Kawabata, Koji S., Nakaoka, Tatsuya, Uemura, Makoto, Imazawa, Ryo, Sasada, Mahito, Akitaya, Hiroshi, Aceituno, Francisco Josè, Bonnoli, Giacomo, Casanova, Vìctor, Myserlis, Ioannis, Sievers, Albrecht, Angelakis, Emmanouil, Kraus, Alexander, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Kang, Sincheol, Kim, Sang-Hyun, Lee, Sang-Sung, Agìs-Gonzàlez, Beatriz, Sota, Alfredo, Escudero, Juan, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kouch, Pouya M., Lindfors, Elina, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Savchenko, Sergey S., Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Swartz, Doug, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We conducted a polarimetry campaign from radio to X-ray wavelengths of the high-synchrotron-peak (HSP) blazar Mrk 421, including Imaging X-ray Polarimetry Explorer (IXPE) measurements on 2022 December 6-8. We detected X-ray polarization of Mrk 421 with a degree of $\Pi_{\rm X}$=14$\pm$1$\%$ and an electric-vector position angle $\psi_{\rm X}$=107$\pm$3$^{\circ}$ in the 2-8 keV band. From the time variability analysis, we find a significant episodic variation in $\psi_{\rm X}$. During 7 months from the first IXPE pointing of Mrk 421 in 2022 May, $\psi_{\rm X}$ varied across the range of 0$^{\circ}$ to 180$^{\circ}$, while $\Pi_{\rm X}$ maintained similar values within $\sim$10-15$\%$. Furthermore, a swing in $\psi_{\rm X}$ in 2022 June was accompanied by simultaneous spectral variations. The results of the multiwavelength polarimetry show that the X-ray polarization degree was generally $\sim$2-3 times greater than that at longer wavelengths, while the polarization angle fluctuated. Additionally, based on radio, infrared, and optical polarimetry, we find that rotation of $\psi$ occurred in the opposite direction with respect to the rotation of $\psi_{\rm X}$ over longer timescales at similar epochs. The polarization behavior observed across multiple wavelengths is consistent with previous IXPE findings for HSP blazars. This result favors the energy-stratified shock model developed to explain variable emission in relativistic jets. The accompanying spectral variation during the $\psi_{\rm X}$ rotation can be explained by a fluctuation in the physical conditions, e.g., in the energy distribution of relativistic electrons. The opposite rotation direction of $\psi$ between the X-ray and longer-wavelength polarization accentuates the conclusion that the X-ray emitting region is spatially separated from that at longer wavelengths., Comment: 17 pages, 13 figures, 4 tables; Accepted for publication in A&A
Published: 2023
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19. X-ray Polarization of the BL Lac Type Blazar 1ES 0229+200

Author: Ehlert, Steven R., Liodakis, Ioannis, Middei, Riccardo, Marscher, Alan P., Tavecchio, Fabrizio, Agudo, Iván, Kouch, Pouya M., Lindfors, Elina, Nilsson, Kari, Myserlis, Ioannis, Gurwell, Mark, Rao, Ramprasad, Aceituno, Francisco Jose, Bonnoli, Giacomo, Casanova, Victor, Agiz-Gonzalez, Beatriz, Escudero, Juan, Santos, Jorge Otero, Sota, Alfredo, Angelakis, Emmanouil, Kraus, Alexander, Keating, Garrett K., Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Negro, Michela, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present polarization measurements in the $2-8 \thinspace \mathrm{keV}$ band from blazar 1ES 0229+200, the first extreme high synchrotron peaked source to be observed by the Imaging X-ray Polarimetry Explorer (IXPE). Combining two exposures separated by about two weeks, we find the degree of polarization to be $\Pi_{X} = 17.9 \pm 2.8 \%$ at an electric-vector position angle $\psi_X = 25.0 \pm 4.6^{\circ}$ using a spectropolarimetric fit from joint IXPE and XMM-Newton observations. There is no evidence for the polarization degree or angle varying significantly with energy or time on both short time scales (hours) or longer time scales (days). The contemporaneous polarization degree at optical wavelengths was $>$7$\times$ lower, making 1ES 0229+200 the most strongly chromatic blazar yet observed. This high X-ray polarization compared to the optical provides further support that X-ray emission in high-peaked blazars originates in shock-accelerated, energy-stratified electron populations, but is in tension with many recent modeling efforts attempting to reproduce the spectral energy distribution of 1ES 0229+200 which attribute the extremely high energy synchrotron and Compton peaks to Fermi acceleration in the vicinity of strongly turbulent magnetic fields., Comment: 17 Pages, 6 Figures, Resubmitted to ApJ after addressing referee comments
Published: 2023

20. 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

21. Thermal properties of the leading hemisphere of Callisto inferred from ALMA observations

Author: Camarca, Maria, de Kleer, Katherine, Butler, Bryan, Akins, Alex B., Thelen, Alexander, de Pater, Imke, Gurwell, Mark A., and Moullet, Arielle
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: We present a thermal observation of Callisto's leading hemisphere obtained using the Atacama Large Millimeter/submillimeter Array (ALMA) at 0.87 mm (343 GHz). The angular resolution achieved for this observation was $\sim$$0.16^{\prime\prime}$, which for Callisto at the time of this observation ($D\sim 1.05^{\prime\prime}$) was equivalent to $\sim$6 elements across the surface. Our disk-integrated brightness temperature of 116 $\pm$ 5 K (8.03 $\pm$ 0.40 Jy) is consistent with prior disk-integrated observations. Global surface properties were derived from the observation using a thermophysical model (de Kleer et al. 2021) constrained by spacecraft data. We find that models parameterized by two thermal inertia components more accurately fit the data than single thermal inertia models. Our best-fit global parameters adopt a lower thermal inertia of 15-50 $\text{J}\:\text{m}^{-2}\:\text{K}^{-1}\:\text{s}^{-1/2}$ and a higher thermal inertia component of 1200-2000 $\text{J}\:\text{m}^{-2}\:\text{K}^{-1}\:\text{s}^{-1/2}$, with retrieved millimeter emissivities of 0.89-0.91. We identify several thermally anomalous regions, including spots $\sim$3 K colder than model predictions co-located with the Valhalla impact basin and a complex of craters in the southern hemisphere; this indicates the presence of materials possessing either a higher thermal inertia or a lower emissivity. A warm region confined to the mid-latitudes in these leading hemisphere data may be indicative of regolith property changes due to exogenic sculpting., Comment: 13 pages, 7 figures
Published: 2023
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22. IXPE and multi-wavelength observations of blazar PG 1553+113 reveal an orphan optical polarization swing

Author: Middei, Riccardo, Perri, Matteo, Puccetti, Simonetta, Liodakis, Ioannis, Di Gesu, Laura, Marscher, Alan P., Cavero, Nicole Rodriguez, Tavecchio, Fabrizio, Donnarumma, Immacolata, Laurenti, Marco, Jorstad, Svetlana G., Agudo, Iván, Marshall, Herman L., Pacciani, Luigi, Kim, Dawoon E., Aceituno, Francisco José, Bonnoli, Giacomo, Casanova, Víctor, Agís-González, Beatriz, Sota, Alfredo, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Sievers, Albrecht, Kouch, Pouya M., Lindfors, Elina, Gurwell, Mark, Keating, Garrett K., Rao, Ramprasad, Kang, Sincheol, Lee, Sang-Sung, Kim, Sang-Hyun, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Angelakis, Emmanouil, Kraus, Alexander, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, García, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Negro, Michela, Ng, Chi-Yung, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The lower energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets. Despite the consensus regarding jet emission processes, the particle acceleration mechanism is still debated. Here, we present the first X-ray polarization observations of PG 1553+113, a high-synchrotron-peak blazar observed by the Imaging X-ray Polarimetry Explorer (IXPE). We detect an X-ray polarization degree of $(10\pm2)\%$ along an electric-vector position angle of $\psi_X=86^{\circ}\pm8^{\circ}$. At the same time, the radio and optical polarization degrees are lower by a factor of $\sim$3. During our IXPE pointing, we observed the first orphan optical polarization swing of the IXPE era, as the optical angle of PG 1553+113 underwent a smooth monotonic rotation by about 125$^\circ$, with a rate of $\sim$17 degrees per day. We do not find evidence of a similar rotation in either radio or X-rays, which suggests that the X-ray and optically emitting regions are separate or, at most, partially co-spatial. Our spectro-polarimetric results provide further evidence that the steady-state X-ray emission in blazars originates in a shock-accelerated and energy-stratified electron population., Comment: Accepted for pubblication in The Astrophysical Journal Letters. 3 Figures, 13 pages
Published: 2023

23. Hidden giants in JWST's PEARLS: An ultra-massive z=4.26 sub-millimeter galaxy that is invisible to HST

Author: Smail, Ian, Dudzeviciute, Ugne, Gurwell, Mark, Fazio, Giovanni G., Willner, S. P., Swinbank, A. M., Arumugam, Vinodiran, Summers, Jake, Cohen, Seth H., Jansen, Rolf A., Windhorst, Rogier A., Meena, Ashish, Zitrin, Adi, Keel, William C., Coe, Dan, Conselice, Christopher J., D'Silva, Jordan C. J., Driver, Simon P., Frye, Brenda, Grogin, Norman A., Koekemoer, Anton M., Marshall, Madeline A., Nonino, Mario, Pirzkal, Nor, Robotham, Aaron, Rutkowski, Michael J., Ryan Jr., Russell E., Tompkins, Scott, Willmer, Christopher N. A., Yan, Haojing, Broadhurst, Thomas J., Cheng, Cheng, Diego, Jose M., Kamieneski, Patrick, and Yun, Min
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: We present a multi-wavelength analysis using SMA, JCMT, NOEMA, JWST, HST, and SST of two dusty strongly star-forming galaxies, 850.1 and 850.2, seen through the massive cluster lens A1489. These SMA-located sources both lie at z=4.26 and have bright dust continuum emission, but 850.2 is a UV-detected Lyman-break galaxy, while 850.1 is undetected at <2um, even with deep JWST/NIRCam observations. We investigate their stellar, ISM, and dynamical properties, including a pixel-level SED analysis to derive sub-kpc-resolution stellar-mass and Av maps. We find that 850.1 is one of the most massive and highly obscured, Av~5, galaxies known at z>4 with M*~10^11.8 Mo (likely forming at z>6), and 850.2 is one of the least massive and least obscured, Av~1, members of the z>4 dusty star-forming population. The diversity of these two dust-mass-selected galaxies illustrates the incompleteness of galaxy surveys at z>3-4 based on imaging at <2um, the longest wavelengths feasible from HST or the ground. The resolved mass map of 850.1 shows a compact stellar mass distribution, Re(mass)~1kpc, but its expected evolution to z~1.5 and then z~0 matches both the properties of massive, quiescent galaxies at z~1.5 and ultra-massive early-type galaxies at z~0. We suggest that 850.1 is the central galaxy of a group in which 850.2 is a satellite that will likely merge in the near future. The stellar morphology of 850.1 shows arms and a linear bar feature which we link to the active dynamical environment it resides within., Comment: Submitted to ApJ, comments welcome!
Published: 2023

24. Millimeter Observations of the Type II SN2023ixf: Constraints on the Proximate Circumstellar Medium

Author: Berger, Edo, Keating, Garrett K., Margutti, Raffaella, Maeda, Keiichi, Alexander, Kate D., Cendes, Yvette, Eftekhari, Tarraneh, Gurwell, Mark, Hiramatsu, Daichi, Ho, Anna Y. Q., Laskar, Tanmoy, Rao, Ramprasad, and Williams, Peter K. G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present 1.3 mm (230 GHz) observations of the recent and nearby Type II supernova, SN2023ixf, obtained with the Submillimeter Array (SMA) at 2.6-18.6 days after explosion. The observations were obtained as part the SMA Large Program POETS (Pursuit of Extragalactic Transients with the SMA). We do not detect any emission at the location of SN2023ixf, with the deepest limits of $L_\nu(230\,{\rm GHz})\lesssim 8.6\times 10^{25}$ erg s$^{-1}$ Hz$^{-1}$ at 2.7 and 7.7 days, and $L_\nu(230\,{\rm GHz})\lesssim 3.4\times 10^{25}$ erg s$^{-1}$ Hz$^{-1}$ at 18.6 days. These limits are about a factor of 2 times dimmer than the mm emission from SN2011dh (IIb), about an order of magnitude dimmer compared to SN1993J (IIb) and SN2018ivc (IIL), and about 30 times dimmer than the most luminous non-relativistic SNe in the mm-band (Type IIb/Ib/Ic). Using these limits in the context of analytical models that include synchrotron self-absorption and free-free absorption we place constraints on the proximate circumstellar medium around the progenitor star, to a scale of $\sim 2\times 10^{15}$ cm, excluding the range $\dot{M}\sim {\rm few}\times 10^{-6}-10^{-2}$ M$_\odot$ yr$^{-1}$ (for a wind velocity, $v_w=115$ km s$^{-1}$, and ejecta velocity, $v_{\rm eje}\sim (1-2)\times 10^4$ km s$^{-1}$). These results are consistent with an inference of the mass loss rate based on optical spectroscopy ($\sim 2\times 10^{-2}$ M$_\odot$ yr$^{-1}$ for $v_w=115$ km s$^{-1}$), but are in tension with the inference from hard X-rays ($\sim 7\times 10^{-4}$ M$_\odot$ yr$^{-1}$ for $v_w=115$ km s$^{-1}$). This tension may be alleviated by a non-homogeneous and confined CSM, consistent with results from high-resolution optical spectroscopy., Comment: Submitted
Published: 2023
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25. Double SSA Spectrum and Magnetic Field Strength of the FSRQ 3C 454.3

Author: Jeong, Hyeon-Woo, Lee, Sang-Sung, Cheong, Whee Yeon, Kim, Jae-Young, Lee, Jee Won, Kang, Sincheol, Kim, Sang-Hyun, Rani, B., Park, Jongho, and Gurwell, Mark A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We present the results of a radio multi-frequency ($\rm 3-340~GHz$) study of the blazar 3C~454.3. After subtracting the quiescent spectrum corresponding to optically thin emission, we found two individual synchrotron self-absorption (SSA) features in the wide-band spectrum. The one SSA had a relatively low turnover frequency ($\nu_{\rm m}$) in the range of $\rm 3-37~GHz$ (lower $\nu_{\rm m}$ SSA spectrum, LSS), and the other one had a relatively high $\nu_{\rm m}$ of $\rm 55-124~GHz$ (higher $\nu_{\rm m}$ SSA spectrum, HSS). Using the SSA parameters, we estimated magnetic field strengths at the surface where optical depth $\tau=1$. The estimated magnetic field strengths were $\rm >7~mG$ and $\rm >0.2~mG$ for the LSS and HSS, respectively. The LSS emitting region was magnetically dominated before the June 2014 $\gamma$-ray flare. The quasi-stationary component (C), $\sim 0.6~{\rm mas}$ apart from the 43 GHz radio core, became brighter than the core with decreasing observing frequency, and we found that component C was related to the LSS. A decrease in jet width was found near component C. As a moving component, K14 approached component C, and the flux density of the component was enhanced while the angular size decreased. The high intrinsic brightness temperature in the fluid frame was obtained as $T_{\rm B, int} \approx (7.0\pm1.0) \times 10^{11}~{\rm K}$ from the jet component after the 2015 August $\gamma$-ray flare, suggesting that component C is a high-energy emitting region. The observed local minimum of jet width and re-brightening behavior suggest a possible recollimation shock in component C., Comment: 16 pages, 12 figures, 5 tables, Accepted for publication in MNRAS
Published: 2023
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26. X-ray Polarization of BL Lacertae in Outburst

Author: Peirson, Abel L., Negro, Michela, Liodakis, Ioannis, Middei, Riccardo, Kim, Dawoon E., Marscher, Alan P., Marshall, Herman L., Pacciani, Luigi, Romani, Roger W., Wu, Kinwah, Di Marco, Alessandro, Di Lalla, Niccolo, Omodei, Nicola, Jorstad, Svetlana G., Agudo, Ivan, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco Jose, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Victor, Garcia-Comas, Maya, Agis-Gonzalez, Beatriz, Husillos, Cesar, Marchini, Alessandro, Sota, Alfredo, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Sievers, Albrecht, Gurwell, Mark, Rao, Ramprasad, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Cheong, Whee Yeon, Jeong, Hyeon-Woo, Kang, Sincheol, Kim, Sang-Hyun, Lee, Sang-Sung, Angelakis, Emmanouil, Kraus, Alexander, Cibrario, Nicolo, Donnarumma, Immacolata, Poutanen, Juri, Tavecchio, Fabrizio, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolo, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kaaret, Philip, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Madejski, Grzegorz, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We report the first $> 99\%$ confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/$\gamma$-ray outburst, a 287 ksec observation (2022 November 27-30) was taken using the Imaging X-ray Polarimetry Explorer ({\it IXPE}), together with contemporaneous multiwavelength observations from the Neil Gehrels {\it Swift} observatory and {\it XMM-Newton} in soft X-rays (0.3--10~keV), {\it NuSTAR} in hard X-rays (3--70~keV), and optical polarization from the Calar Alto, and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the {\it IXPE} energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find $>99\%$ confidence X-ray polarization $\Pi_{2-4{\rm keV}} = 21.7^{+5.6}_{-7.9}\%$ and electric vector polarization angle $\psi_{2-4{\rm keV}} = -28.7 \pm 8.7^{\circ}$ in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous {\it IXPE} BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs., Comment: Accepted to ApJL. 16 pages, 8 figures
Published: 2023
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27. Discovery of X-ray polarization angle rotation in active galaxy Mrk 421

Author: Di Gesu, Laura, Marshall, Herman L., Ehlert, Steven R., Kim, Dawoon E., Donnarumma, Immacolata, Tavecchio, Fabrizio, Liodakis, Ioannis, Kiehlmann, Sebastian, Agudo, Iván, Jorstad, Svetlana G., Muleri, Fabio, Marscher, Alan P., Puccetti, Simonetta, Middei, Riccardo, Perri, Matteo, Pacciani, Luigi, Negro, Michela, Romani, Roger W., Di Marco, Alessandro, Blinov, Dmitry, Bourbah, Ioakeim G., Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Gurwell, Mark, Rao, Ramprasad, Keating, Garrett, Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco Josè, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Vìctor, Garcìa-Comas, Maya, Agìs-Gonzàlez, Beatriz, Husillos, Cèsar, Marchini, Alessandro, Sota, Alfredo, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Savchenko, Sergey S., Vasilyev, Andrey A., Gòmez, Josè L., Antonelli, Lucio A., Barnouin, Thibault, Bonino, Raffaella, Cavazzuti, Elisabetta, Costamante, Luigi, Chen, Chien-Ting, Cibrario, Nicolò, De Rosa, Alessandra, Di Pierro, Federico, Errando, Manel, Kaaret, Philip, Karas, Vladimir, Krawczynski, Henric, Lisalda, Lindsey, Madejski, Grzegorz, Malacaria, Christian, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, O'Dell, Stephen L., Paggi, Alessandro, Peirson, Abel L., Petrucci, Pierre-Olivier, Ramsey, Brian D., Tennant, Allyn F., Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Ng, C. -Y., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The magnetic field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle $\Psi$. Here we report the discovery of a $\Psi_{\mathrm x}$ rotation in the X-ray band in the blazar Mrk 421 at an average flux state. Across the 5 days of Imaging X-ray Polarimetry Explorer (IXPE) observations of 4-6 and 7-9 June 2022, $\Psi_{\mathrm x}$ rotated in total by $\geq360^\circ$. Over the two respective date ranges, we find constant, within uncertainties, rotation rates ($80 \pm 9$ and $91 \pm 8 ^\circ/\rm day$) and polarization degrees ($\Pi_{\mathrm x}=10\%\pm1\%$). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray emitting site does not completely overlap the radio/infrared/optical emission sites, as no similar rotation of $\Psi$ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region likely lies in a sheath surrounding an inner spine where the X-ray radiation is released.
Published: 2023

28. Testing the linear relationship between black hole mass and variability timescale in low-luminosity AGN at submillimeter wavelengths

Author: Chen, Bo-Yan, Bower, Geoffrey C., Dexter, Jason, Markoff, Sera, Ridenour, Anthony, Gurwell, Mark A., Rao, Ramprasad, and Wallström, Sofia H. J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The variability of submillimeter emission provides a useful tool to probe the accretion physics in low-luminosity active galactic nuclei. We accumulate four years of observations using Submillimeter Array for Centaurus A, NGC 4374, NGC 4278, and NGC 5077 and one year of observations for NGC 4552 and NGC 4579. All sources are variable. We measure the characteristic timescale at which the variability is saturated by modeling these sources' light curve as a damped random walk. We detect a timescale for all the sources except NGC 4552. The detected timescales are comparable to the orbital timescale at the event horizon scale for most sources. Combined with previous studies, we show a correlation between the the timescale and the black hole mass over three orders of magnitude. This discovery suggests the sub-mm emission is optically thin with the emission originating from the event horizon. The mass scaling relationship further suggests that a group of radio sources with a broadband spectrum that peaks at submillimeter wavelengths have similar inner accretion physics. Sources that follow this relationship may be good targets for high-resolution imaging with the Event Horizon Telescope., Comment: 18 pages, 7 figures, 4 tables, accepted for publication by ApJ
Published: 2023
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29. 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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30. Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE

Author: Veledina, Alexandra, Muleri, Fabio, Poutanen, Juri, Podgorný, Jakub, Dovčiak, Michal, Capitanio, Fiamma, Churazov, Eugene, De Rosa, Alessandra, Di Marco, Alessandro, Forsblom, Sofia, Kaaret, Philip, Krawczynski, Henric, La Monaca, Fabio, Loktev, Vladislav, Lutovinov, Alexander A., Molkov, Sergey V., Mushtukov, Alexander A., Ratheesh, Ajay, Cavero, Nicole Rodriguez, Steiner, James F., Sunyaev, Rashid A., Tsygankov, Sergey S., Zdziarski, Andrzej A., Bianchi, Stefano, Bright, Joe S., Bursov, Nikolaj, Costa, Enrico, Egron, Elise, Garcia, Javier A., Green, David A., Gurwell, Mark, Ingram, Adam, Kajava, Jari J. E., Kale, Ruta, Kraus, Alex, Malyshev, Denys, Marin, Frédéric, Matt, Giorgio, McCollough, Michael, Mereminskiy, Ilia A., Nizhelsky, Nikolaj, Piano, Giovanni, Pilia, Maura, Pittori, Carlotta, Rao, Ramprasad, Righini, Simona, Soffitta, Paolo, Shevchenko, Anton, Svoboda, Jiri, Tombesi, Francesco, Trushkin, Sergei, Tsybulev, Peter, Ursini, Francesco, Weisskopf, Martin C., Wu, Kinwah, Agudo, Iván, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Donnarumma, Immacolata, Doroshenko, Victor, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Negro, Michela, Ng, Chi-Yung, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Roberts, Oliver, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Swartz, Doug, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Trois, Alessio, Turolla, Roberto, Vink, Jacco, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: The accretion of matter by compact objects can be inhibited by radiation pressure if the luminosity exceeds the critical value, known as the Eddington limit. Discovery of ultraluminous X-ray sources has shown that accretion can proceed even when the apparent luminosity significantly exceeds this limit. High apparent luminosity might be produced thanks to geometric beaming of the radiation by an outflow. The outflow half-opening angle, which determines the amplification due to beaming, has never been robustly constrained. Using the Imaging X-ray Polarimetry Explorer, we made the measurement of X-ray polarization in the Galactic X-ray binary Cyg X-3. We find high, over 20%, nearly energy-independent linear polarization, orthogonal to the direction of the radio ejections. These properties unambiguously indicate the presence of a collimating outflow in the X-ray binary Cyg~X-3 and constrain its half-opening angle, <15 degrees. Thus, the source can be used as a laboratory for studying the super-critical accretion regime. This finding underscores the importance of X-ray polarimetry in advancing our understanding of accreting sources., Comment: 52 pages, 14 figures, 3 tables. Author version of the article published in Nature Astronomy
Published: 2023
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31. 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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32. X-ray Polarization Observations of BL Lacertae

Author: Middei, Riccardo, Liodakis, Ioannis, Perri, Matteo, Puccetti, Simonetta, Cavazzuti, Elisabetta, Di Gesu, Laura, Ehlert, Steven R., Madejski, Grzegorz, Marscher, Alan P., Marshall, Herman L., Muleri, Fabio, Negro, Michela, Jorstad, Svetlana G., Agís-González, Beatriz, Agudo, Iván, Bonnoli, Giacomo, Bernardos, Maria I., Casanova, Víctor, García-Comas, Maya, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Kouch, Pouya M., Borman, George A., Kopatskaya, Evgenia N., Larionova, Elena G., Morozova, Daria A., Savchenko, Sergey S., Vasilyev, Andrey A., Zhovtan, Alexey V., Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Hales, Antonio, Kameno, Seiji, Kneissl, Ruediger, Messias, Hugo, Nagai, Hiroshi, Blinov, Dmitry, Bourbah, Ioakeim G., Kiehlmann, Sebastian, Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Masiero, Joseph R., Mawet, Dimitri, Millar-Blanchaer, Maxwell A., Panopoulou, Georgia V., Tinyanont, Samaporn, Berdyugin, Andrei V., Kagitani, Masato, Kravtsov, Vadim, Sakanoi, Takeshi, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Gurwell, Mark, Rao, Ramprasad, Di Lalla, Niccoló, Cibrario, Nicoló, Donnarumma, Immacolata, Kim, Dawoon E., Omodei, Nicola, Pacciani, Luigi, Poutanen, Juri, Tavecchio, Fabrizio, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Marco, Alessandro, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $\Pi_X<$12.6\% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac., Comment: 17 pages, 5 figures, accepted for publication in ApJL
Published: 2022
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33. Resolving the inner parsec of the blazar J1924-2914 with the Event Horizon Telescope

Author: Issaoun, Sara, Wielgus, Maciek, Jorstad, Svetlana, Krichbaum, Thomas P., Blackburn, Lindy, Janssen, Michael, Chan, Chi-Kwan, Pesce, Dominic W., Gomez, Jose L., Akiyama, Kazunori, Moscibrodzka, Monika, Marti-Vidal, Ivan, Chael, Andrew, Lico, Rocco, Liu, Jun, Ramakrishnan, Venkatessh, Lisakov, Mikhail, Fuentes, Antonio, Zhao, Guang-Yao, Moriyama, Kotaro, Broderick, Avery E., Tiede, Paul, MacDonald, Nicholas R., Mizuno, Yosuke, Traianou, Efthalia, Loinard, Laurent, Davelaar, Jordy, Gurwell, Mark, Lu, Ru-Sen, and Collaboration, Event Horizon Telescope
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The blazar J1924-2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic Center's black hole Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with the unprecedented 20 $\mu$as resolution of the EHT. J1924-2914 is a very compact flat-spectrum radio source with strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the EHT (April 5-11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28), giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations probe jet properties from the subparsec to 100-parsec scales. We combine the multi-frequency images of J1924-2914 to study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise rotation of the jet projected position angle of about 90 degrees between 2.3 and 230 GHz. Linearly polarized intensity images of J1924-2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal magnetic fields in the blazar compact core.
Published: 2022
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34. Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign

Author: Wielgus, Maciek, Marchili, Nicola, Marti-Vidal, Ivan, Keating, Garrett K., Ramakrishnan, Venkatessh, Tiede, Paul, Fomalont, Ed, Issaoun, Sara, Neilsen, Joey, Nowak, Michael A., Blackburn, Lindy, Gammie, Charles F., Goddi, Ciriaco, Haggard, Daryl, Lee, Daeyoung, Moscibrodzka, Monika, Tetarenko, Alexandra J., Bower, Geoffrey C., Chan, Chi-Kwan, Chatterjee, Koushik, Chesler, Paul M., Dexter, Jason, Doeleman, Sheperd S., Georgiev, Boris, Gurwell, Mark, Johnson, Michael D., Marrone, Daniel P., Mus, Alejandro, Psaltis, Dimitrios, Ripperda, Bart, and Collaboration, Gunther Witzel + the Event Horizon Telescope
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5-11 in the 1.3 millimeter wavelength band. At the same time, interferometric array data from the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array were collected, providing Sgr A* light curves simultaneous with the EHT observations. These data sets, complementing the EHT very-long-baseline interferometry, are characterized by a cadence and signal-to-noise ratio previously unattainable for Sgr A* at millimeter wavelengths, and they allow for the investigation of source variability on timescales as short as a minute. While most of the light curves correspond to a low variability state of Sgr A*, the April 11 observations follow an X-ray flare, and exhibit strongly enhanced variability. All of the light curves are consistent with a red noise process, with a power spectral density (PSD) slope measured to be between -2 and -3 on timescales between 1 min and several hours. Our results indicate a steepening of the PSD slope for timescales shorter than 0.3 h. The spectral energy distribution is flat at 220 GHz and there are no time-lags between the 213 and 229 GHz frequency bands, suggesting low optical depth for the event horizon scale source. We characterize Sgr A*'s variability, highlighting the different behavior observed just after the X-ray flare, and use Gaussian process modeling to extract a decorrelation timescale and a PSD slope. We also investigate the systematic calibration uncertainties by analyzing data from independent data reduction pipelines.
Published: 2022
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35. Discovery of X-ray polarization angle rotation in the jet from blazar Mrk 421

Author: Di Gesu, Laura, Marshall, Herman L., Ehlert, Steven R., Kim, Dawoon E., Donnarumma, Immacolata, Tavecchio, Fabrizio, Liodakis, Ioannis, Kiehlmann, Sebastian, Agudo, Iván, Jorstad, Svetlana G., Muleri, Fabio, Marscher, Alan P., Puccetti, Simonetta, Middei, Riccardo, Perri, Matteo, Pacciani, Luigi, Negro, Michela, Romani, Roger W., Di Marco, Alessandro, Blinov, Dmitry, Bourbah, Ioakeim G., Kontopodis, Evangelos, Mandarakas, Nikos, Romanopoulos, Stylianos, Skalidis, Raphael, Vervelaki, Anna, Casadio, Carolina, Escudero, Juan, Myserlis, Ioannis, Gurwell, Mark A., Rao, Ramprasad, Keating, Garrett K., Kouch, Pouya M., Lindfors, Elina, Aceituno, Francisco José, Bernardos, Maria I., Bonnoli, Giacomo, Casanova, Víctor, García-Comas, Maya, Agís-González, Beatriz, Husillos, César, Marchini, Alessandro, Sota, Alfredo, Imazawa, Ryo, Sasada, Mahito, Fukazawa, Yasushi, Kawabata, Koji S., Uemura, Makoto, Mizuno, Tsunefumi, Nakaoka, Tatsuya, Akitaya, Hiroshi, Savchenko, Sergey S., Vasilyev, Andrey A., Gómez, José L., Antonelli, Lucio A., Barnouin, Thibault, Bonino, Raffaella, Cavazzuti, Elisabetta, Costamante, Luigi, Chen, Chien-Ting, Cibrario, Nicolò, De Rosa, Alessandra, Di Pierro, Federico, Errando, Manel, Kaaret, Philip, Karas, Vladimir, Krawczynski, Henric, Lisalda, Lindsey, Madejski, Grzegorz, Malacaria, Christian, Marin, Frédéric, Marinucci, Andrea, Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, O’Dell, Stephen L., Paggi, Alessandro, Peirson, Abel L., Petrucci, Pierre-Olivier, Ramsey, Brian D., Tennant, Allyn F., Wu, Kinwah, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, Costa, Enrico, Del Monte, Ettore, Di Lalla, Niccolò, Doroshenko, Victor, Dovčiak, Michal, Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Ng, C.-Y., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Xie, Fei, and Zane, Silvia
Published: 2023
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36. A double-period oscillation signal in millimeter emission of the radio galaxy NGC 1275

Author: Zhang, Pengfei, Wang, Zhongxiang, Gurwell, Mark, and Wiita, Paul J.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The nearby Seyfert type galaxy NGC 1275 contains a bright radio nucleus at its center, revealed through high-spatial resolution imaging to be the source of the jets emanating from the galaxy. Coincident with the emergence of a new component C3 in the nucleus since 2005, flux densities from NGC 1275, at least at radio, millimeter (mm), and gamma-ray frequencies, had been increasing up through 2017 and leveled off afterwards. We analyze the long-term light curves of the nucleus that span the rising trend to 2015 July, and find a pair of approximately year-long quasi-periodic oscillations, with periods of $P_l\simeq 345$\,d and $P_h\simeq 386$\,d respectively, in emission at 1.3-mm wavelength. We discuss the case that there would be a long precession period $P_{\rm prec}\simeq 9$\,yr, causing the appearance of $P_h$ that is slightly higher than $P_l$. The accretion disk around the central supermassive black hole (SMBH) would be precessing at $P_{\rm prec}$, induced by either the Lense-Thirring effect or the existence of a companion SMBH. In the two scenarios, $P_l$ would be the jet wobbling timescale or the SMBH binary period respectively. The finding, which could be verified through high-spatial resolution mm imaging, would not only identify the nature of the jet variation but also help reveal the full features of the galaxy., Comment: 12 pages, 8 figures, accepted for publication in ApJ
Published: 2021
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37. On the Origin of Gamma-ray Flares from Bright Fermi Blazars

Author: Paliya, Vaidehi S., Boettcher, Markus, Gurwell, Mark, and Stalin, C. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The origin of gamma-ray flares observed from blazars is one of the major mysteries in jet physics. We have attempted to address this problem following a novel spectral energy distribution (SED) fitting technique that explored the flaring patterns identified in the broadband SEDs of two gamma-ray bright blazars 3C 279 (z=0.54) and 3C 454.3 (z=0.86), using near-simultaneous radio-to-gamma-ray observations. For both sources, the gamma-ray flux strongly correlates with the separation of the SED peaks and the Compton dominance. We propose that spectral hardening of the radiating electron population and/or enhancement of the Doppler factor can naturally explain these observations. In both cases, magnetic reconnection may play a pivotal role in powering the luminous gamma-ray flares., Comment: ApJS, in press
Published: 2021
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38. 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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39. Radio and $\gamma$-ray activity in the jet of the blazar S5 0716$+$714

Author: Kim, Dae-Won, Kravchenko, Evgeniya V., Kutkin, Alexander M., Böttcher, Markus, Gómez, José L., Gurwell, Mark, Jorstad, Svetlana G., Lähteenmäki, Anne, Marscher, Alan P., Ramakrishnan, Venkatessh, Tornikoski, Merja, Trippe, Sascha, Weaver, Zachary, and Williamson, Karen E.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: We explore the connection between the $\gamma$-ray and radio emission in the jet of the blazar 0716$+$714 by using 15, 37, and 230 GHz radio and 0.1$-$200 GeV $\gamma$-ray light curves spanning 10.5 years (2008$-$2019). We find significant positive and negative correlations between radio and $\gamma$-ray fluxes in different time ranges. The time delays between radio and $\gamma$-ray emission suggest that the observed $\gamma$-ray flares originated from multiple regions upstream of the radio core, within a few parsecs from the central engine. Using time-resolved 43 GHz VLBA maps we identified 14 jet components moving downstream along the jet. Their apparent speeds range from 6 to 26 $c$, showing notable variations in their position angles upstream the stationary component ($\sim$0.53 mas from the core). The brightness temperature declines as function of distance from the core according to a power-law which becomes shallower at the location of the stationary component. We also find that the periods at which significant correlations between radio and $\gamma$-ray emission occur overlap with the times when the jet was oriented to the north. Our results indicate that the passage of a propagating disturbance (or shock) through the radio core and the orientation of the jet might be responsible for the observed correlation between the radio and $\gamma$-ray variability. We present a scenario that connects the positive correlation and the unusual anti-correlation by combining the production of a flare and a dip at $\gamma$-rays by a strong moving shock at different distances from the jet apex., Comment: 26 pages, 13 figures, 5 tables, Accepted for publication in ApJ
Published: 2021
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40. 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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41. Morphological transition of the compact radio lobe in 3C84 via the strong jet-cloud collision

Author: Kino, Motoki, Niinuma, Kotaro, Kawakatu, Nozomu, Nagai, Hiroshi, Giovannini, Gabriele, Orienti, Monica, Wajima, Kiyoaki, D'Ammando, Filippo, Hada, Kazuhiro, Giroletti, Marcello, and Gurwell, Mark
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report multi-epoch Very Long Baseline Interferometric (VLBI) observations of the compact radio lobe in the radio galaxy 3C84 (NGC1275) during 2016 - 2020. The image sequence of 3C84 reveals that the hotspot in the radio lobe showed the one-year long frustration in 2017 within a compact region of about 0.07 parsec, suggesting a strong collision between the jet and a compact dense cloud with the estimated average density about $(4\-- 6)\times 10^{5}~{\rm cm^{-3}}$. Although the hotspot and the radio lobe began to move south again after its breakout, the radio lobe showed a morphological transition from FR II- to FR I-class radio lobe and its radio flux became fainter. This is the first detection of the dynamical feedback from the cloud to the jet where the cloud located on the jet axis significantly interferes with the jet propagation and evolution at the central one-parsec region in active galactic nucleus., Comment: The Astrophysical Journal Letters, Volume 920, Issue 1, id.L24, 7 pp
Published: 2021

42. Microwave spectra of the leading and trailing hemispheres of Iapetus

Author: Bonnefoy, Léa E., Lellouch, Emmanuel, Le Gall, Alice, Lestrade, Jean-François, Moreno, Raphaël, Butler, Bryan, Boissier, Jérémie, Leyrat, Cédric, Sultana, Robin, Cavalié, Thibault, Gurwell, Mark, Moullet, Arielle, Ladjelate, Bilal, and Ponthieu, Nicolas
Published: 2024
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43. 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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44. 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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45. Ganymede's Surface Properties from Millimeter and Infrared Thermal Emission

Author: de Kleer, Katherine, Butler, Bryan, de Pater, Imke, Gurwell, Mark A., Moullet, Arielle, Trumbo, Samantha, and Spencer, John
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: We present thermal observations of Ganymede from the Atacama Large Millimeter Array (ALMA) in 2016-2019 at a spatial resolution of 300-900 km (0.1-0.2'' angular resolution) and frequencies of 97.5, 233, and 343.5 GHz (wavelengths of 3, 1.3, and 0.87 mm); the observations collectively covered all Ganymede longitudes. We determine the global thermophysical properties using a thermal model that considers subsurface emission and depth- and temperature-dependent thermophysical and dielectric properties, in combination with a retrieval algorithm. The data are sensitive to emission from the upper $\sim$0.5 meter of the surface, and we find a millimeter emissivity of 0.75-0.78 and (sub)surface porosities of 10-40%, corresponding to effective thermal inertias of 400-800 J m^{-2} K^{-1} s^{-1/2}. Combined with past infrared results, as well as modeling presented here of a previously-unpublished Galileo PPR nighttime infrared observation, the multi-wavelength constraints are consistent with a compaction profile whereby the porosity drops from ~85% at the surface to 10{+30/-10}% at depth over a compaction length scale of tens of cm. We present maps of temperature residuals from the best-fit global models which indicate localized variations in thermal surface properties at some (but not all) dark terrains and at impact craters, which appear 5-8 K colder than the model. Equatorial regions are warmer than predicted by the model, in particular near the centers of the leading and trailing hemispheres, while the mid-latitudes (~30-60 degrees) are generally colder than predicted; these trends are suggestive of an exogenic origin., Comment: Fixed typo in Eqn 1; article published in Planetary Science Journal, Vol 2, Issue 1, id.5 (Feb 2021)
Published: 2021

46. The optical-gamma correlation in BL Lacertae

Author: Raiteri Claudia M., Villata Massimo, D’Ammando Filippo, Larionov Valeri M., Gurwell Mark A., Mirzaqulov Davron O., Smith Paul S., and Carnerero Maria Isabel
Subjects: Physics, QC1-999
Abstract: We present multifrequency light curves of BL Lacertae from February 2008 to October 2012. Lowenergy data (optical and millimetre) were acquired in the framework of a GASP-WEBT project. High-energy data (ultraviolet, X-ray, and γ-ray) come from observations of the Swift, RXTE, and Fermi satellites. After a period of moderate activity, in May 2011 the source suddenly started to flare at γ and optical-UV frequencies. Activity at millimetre wavelengths and X rays began 3-4 months later. This behaviour offered a good opportunity to study the correlation among flux variability in different bands, in particular between the best-sampled optical and γ-ray light curves. However, even in this fortuitous case, we can only define a general correlation with likely no time lag, but with a lag uncertainty of ±1 day. Indeed, the data reveal a complex relationship between the γ and optical fluxes, which cannot be unveiled because of the small gaps in the sampling of this extremely variable source.
Published: 2013
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47. No evidence of phosphine in the atmosphere of Venus by independent analyses

Author: Villanueva, Geronimo, Cordiner, Martin, Irwin, Patrick, de Pater, Imke, Butler, Bryan, Gurwell, Mark, Milam, Stefanie, Nixon, Conor, Luszcz-Cook, Statia, Wilson, Colin, Kofman, Vincent, Liuzzi, Giuliano, Faggi, Sara, Fauchez, Thomas, Lippi, Manuela, Cosentino, Richard, Thelen, Alexander, Moullet, Arielle, Hartogh, Paul, Molter, Edward, Charnley, Steve, Arney, Giada, Mandell, Avi, Biver, Nicolas, Vandaele, Ann, de Kleer, Katherine, and Kopparapu, Ravi
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The detection of phosphine (PH3) in the atmosphere of Venus has been recently reported based on millimeter-wave radio observations (Greaves et al. 2020), and its re-analyses (Greaves et al. 2021a/b). In this Matters Arising we perform an independent reanalysis, identifying several issues in the interpretation of the spectroscopic data. As a result, we determine sensitive upper-limits for PH3 in Venus' atmosphere (>75 km, above the cloud decks) that are discrepant with the findings in G2020 and G2021a/b. The measurements target the fundamental first rotational transition of PH3 (J=1-0) at 266.944513 GHz, which was observed with the James Clerk Maxwell Telescope (JCMT) in June 2017 and with the Atacama Large Millimeter/submillimeter Array (ALMA) in March 2019. This line's center is near the SO2 (J=309,21-318,24) transition at 266.943329 GHz (only 1.3 km/s away from the PH3 line) which represents a potential source of contamination. The JCMT and ALMA data, as presented in G2020, are at spectral resolutions comparable to the frequency separation of the two lines. Moreover, the spectral features identified are several km/s in width, and therefore do not permit distinct spectroscopic separation of the candidate spectral lines of PH3 and SO2. We present the radiative transfer modelling we have performed and then discuss the ALMA and JCMT analyses in turn.
Published: 2020
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48. 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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49. Interferometric Monitoring of Gamma-ray Bright AGNs: OJ 287

Author: Lee, Jee Won, Lee, Sang-Sung, Algaba, Juan-Carlos, Hodgson, Jeffrey, Kim, Jae-Young, Park, Jongho, Kino, Motoki, Kim, Dae-Won, Kang, Sincheol, Yoo, Sungmin, Kim, Sang Hyun, and Gurwell, Mark
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of simultaneous multi-frequency imaging observations at 22, 43, 86, and 129\,GHz of OJ\,287. We used the Korean VLBI Network as part of the Interferometric MOnitoring of GAmma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15\,GHz OVRO and 225\,GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated time scales of three flux enhancements were similar with time scales of $\sim$50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225\,GHz enhancements led the 15\,GHz enhancements by a range of 7 to 30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86\,GHz. We could reliably measure the turnover frequency, $\nu_{\rm c}$, of the core of the source in three epochs. This was measured to be in a range from 27 to 50\,GHz and a flux density at the turnover frequency, $S_{\rm m}$, ranging from 3-6\,Jy. The derived SSA magnetic fields, $B_{\rm SSA}$, are in a range from $0.157\pm0.104$ to $0.255\pm0.146$ mG. We estimated the equipartition magnetic field strengths to be in a range from $0.95\pm0.15$ to $1.93\pm0.30$ mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of $B_{\rm SSA}$. We conclude that the downstream jet may be more particle energy dominated., Comment: 27 pages, 9 figures, Accepted for publication in ApJ
Published: 2020
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50. Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) -- Full Data Release

Author: Stephens, Ian W., Bourke, Tyler L., Dunham, Michael M., Myers, Philip C., Pokhrel, Riwaj, Tobin, John J., Arce, Héctor G., Sadavoy, Sarah I., Vorobyov, Eduard I., Pineda, Jaime E., Offner, Stella S. R., Lee, Katherine I., Kristensen, Lars E., Jørgensen, Jes K., Gurwell, Mark A., and Goodman, Alyssa A.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Abstract: We present and release the full dataset for the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. This survey used the Submillimeter Array (SMA) to image the 74 known protostars within the Perseus molecular cloud. The SMA was used in two array configurations to capture outflows for scales $>$30$^{\prime\prime}$ ($>$9000 au) and to probe scales down to $\sim$1$^{\prime\prime}$ ($\sim$300 au). The protostars were observed with the 1.3 mm and 850 $\mu$m receivers simultaneously to detect continuum at both wavelengths and molecular line emission from CO(2-1), $^{13}$CO(2-1), C$^{18}$O(2-1), N$_2$D$^+$(3-2), CO(3-2), HCO$^+$(4-3), and H$^{13}$CO$^+$(4-3). Some of the observations also used the SMA's recently upgraded correlator, SWARM, whose broader bandwidth allowed for several more spectral lines to be observed (e.g., SO, H$_2$CO, DCO$^+$, DCN, CS, CN). Of the main continuum and spectral tracers observed, 84% of the images and cubes had emission detected. The median C$^{18}$O(2-1) linewidth is $\sim$1.0 km s$^{-1}$, which is slightly higher than those measured with single-dish telescopes at scales of 3000-20000 au. Of the 74 targets, six are suggested to be first hydrostatic core candidates, and we suggest that L1451-mm is the best candidate. We question a previous continuum detection toward L1448 IRS2E. In the SVS13 system, SVS13A certainly appears to be the most evolved source, while SVS13C appears to be hotter and more evolved than SVS13B. The MASSES survey is the largest publicly available interferometric continuum and spectral line protostellar survey to date, and is largely unbiased as it only targets protostars in Perseus. All visibility ($uv$) data and imaged data are publicly available at https://dataverse.harvard.edu/dataverse/full_MASSES/., Comment: Accepted to ApJS
Published: 2019
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