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4,204 results on '"MANFREDA A"'

51. X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: an in-depth study with IXPE and NuSTAR

Author: Ursini, F., Farinelli, R., Gnarini, A., Poutanen, J., Bianchi, S., Capitanio, F., Di Marco, A., Fabiani, S., La Monaca, F., Malacaria, C., Matt, G., Mikušincová, R., Cocchi, M., Kaaret, P., Kajava, J. J. E., Pilia, M., Zhang, W., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Castellano, S., Cavazzuti, E., Chen, C. -T., Ciprini, S., Costa, E., De Rosa, A., Del Monte, E., Di Gesu, L., Di Lalla, N., Donnarumma, I., Doroshenko, V., Dovčiak, M., Ehlert, S. R., Enoto, T., Evangelista, Y., Ferrazzoli, R., Garcia, J. A., Gunji, S., Hayashida, K., Heyl, J., Iwakiri, W., Jorstad, S. G., Karas, V., Kislat, F., Kitaguchi, T., Kolodziejczak, J. J., Krawczynski, H., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marin, F., Marinucci, A., Marscher, A. P., Marshall, H. L., Massaro, F., Mitsuishi, I., Mizuno, T., Muleri, F., Negro, M., Ng, C. -Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Petrucci, P. -O., Possenti, A., Puccetti, S., Ramsey, B. D., Rankin, J., Ratheesh, A., Roberts, O. J., Romani, R. W., Sgrò, C., Slane, P., Soffitta, P., Spandre, G., Swartz, D. A., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Tombesi, F., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: We report on a comprehensive analysis of simultaneous X-ray polarimetric and spectral data of the bright atoll source GX 9+9 with the Imaging X-ray Polarimetry Explorer (IXPE) and NuSTAR. The source is significantly polarized in the 4--8 keV band, with a degree of $2.2\% \pm 0.5\%$ (uncertainty at the 68% confidence level). The NuSTAR broad-band spectrum clearly shows an iron line, and is well described by a model including thermal disk emission, a Comptonized component, and reflection. From a spectro-polarimetric fit, we obtain an upper limit to the polarization degree of the disk of 4% (at 99% confidence level), while the contribution of Comptonized and reflected radiation cannot be conclusively separated. However, the polarization is consistent with resulting from a combination of Comptonization in a boundary or spreading layer, plus reflection off the disc, which gives a significant contribution in any realistic scenario., Comment: 10 pages, accepted for publication in A&A
Published: 2023
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52. Complex variations of X-ray polarization in the X-ray pulsar LS V +44 17/RX J0440.9+4431

Author: Doroshenko, Victor, Poutanen, Juri, Heyl, Jeremy, Tsygankov, Sergey S., Caiazzo, Ilaria, Turolla, Roberto, Veledina, Alexandra, Weisskopf, Martin C., Forsblom, Sofia V., González-Caniulef, Denis, Loktev, Vladislav, Malacaria, Christian, Mushtukov, Alexander A., Suleimanov, Valery F., Lutovinov, Alexander A., Mereminskiy, Ilya A., Molkov, Sergey V., Salganik, Alexander, Santangelo, Andrea, Berdyugin, Andrei V., Kravtsov, Vadim, Nitindala, Anagha P., Agudo, Iván, 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, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, García, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., 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., 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., Sgrò, 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, Vink, Jacco, Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on Imaging X-ray polarimetry explorer (IXPE) observations of the Be-transient X-ray pulsar LS V +44 17/RX J0440.9+4431 made at two luminosity levels during the giant outburst in January--February 2023. Considering the observed spectral variability and changes in the pulse profiles, the source was likely caught in supercritical and subcritical states with significantly different emission-region geometry, associated with the presence of accretion columns and hot spots, respectively. We focus here on the pulse-phase-resolved polarimetric analysis and find that the observed dependencies of the polarization degree and polarization angle (PA) on the pulse phase are indeed drastically different for the two observations. The observed differences, if interpreted within the framework of the rotating vector model (RVM), imply dramatic variations in the spin axis inclination, the position angle, and the magnetic colatitude by tens of degrees within the space of just a few days. We suggest that the apparent changes in the observed PA phase dependence are predominantly related to the presence of an unpulsed polarized component in addition to the polarized radiation associated with the pulsar itself. We then show that the observed PA phase dependence in both observations can be explained with a single set of RVM parameters defining the pulsar's geometry. We also suggest that the additional polarized component is likely produced by scattering of the pulsar radiation in the equatorial disk wind., Comment: 10 pages, 7 figures, accepted in A&A
Published: 2023
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53. X-ray polarimetry of the accreting pulsar GX 301-2

Author: Suleimanov, Valery F., Forsblom, Sofia V., Tsygankov, Sergey S., Poutanen, Juri, Doroshenko, Victor, Doroshenko, Rosalia, Capitanio, Fiamma, Di Marco, Alessandro, González-Caniulef, Denis, Heyl, Jeremy, La Monaca, Fabio, Lutovinov, Alexander A., Molkov, Sergey V., Malacaria, Christian, Mushtukov, Alexander A., Shtykovsky, Andrey E., Agudo, Iván, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Donnarumma, Immacolata, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., 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., Perri, Matteo, Rollins, Melissa Pesce, Petrucci, Pierre Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, 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, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The phase- and energy-resolved polarization measurements of accreting X-ray pulsars (XRPs) allow us to test different theoretical models of their emission, and they also provide an avenue to determine the emission region geometry. We present the results of the observations of the XRP GX 301-2 performed with the Imaging X-ray Polarimetry Explorer (IXPE). A persistent XRP, GX 301-2 has one of the longest spin periods known: $\sim$680s. A massive hyper-giant companion star Wray 977 supplies mass to the neutron star via powerful stellar winds. We did not detect significant polarization in the phase-averaged data when using spectro-polarimetric analysis, with the upper limit on the polarization degree (PD) of 2.3% (99% confidence level). Using the phase-resolved spectro-polarimetric analysis, we obtained a significant detection of polarization (above 99% confidence level) in two out of nine phase bins and a marginal detection in three bins, with a PD ranging between $\sim$3% and $\sim$10% and a polarization angle varying in a very wide range from $\sim$0 degree to $\sim$160 degree. Using the rotating vector model, we obtained constraints on the pulsar geometry using both phase-binned and unbinned analyses, finding excellent agreement. Finally, we discuss possible reasons for a low observed polarization in GX 301-2., Comment: 10 pages, 10 figures, accepted for publication in A&A
Published: 2023
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54. 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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55. 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

56. The X-ray polarisation of the Seyfert 1 galaxy IC 4329A

Author: Ingram, A., Ewing, M., Marinucci, A., Tagliacozzo, D., Rosario, D. J., Veledina, A., Kim, D. E., Marin, F., Bianchi, S., Poutanen, J., Matt, G., Marshall, H. L., Ursini, F., De Rosa, A., Petrucci, P-O., Madejski, G., Barnouin, T., Di Gesu, L., Dovvciak, M., Gianolli, V. E., Krawczynski, H., Loktev, V., Middei, R., Podgorny, J., Puccetti, S., Ratheesh, A., Soffitta, P., Tombesi, F., Ehlert, S. R., Massaro, F., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Chen, C. -T., Ciprini, S., Costa, E., Del Monte, E., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., Garcia, J. A., Gunji, S., Heyl, J., Iwakiri, W., Jorstad, S. G., Kaaret, P., Karas, V., Kislat, F., Kitaguchi, T., Kolodziejczak, J. J., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marscher, A. P., Mitsuishi, I., Mizuno, T., Muleri, F., Negro, M., Ng, C. -Y., ODell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Pilia, M., Possenti, A., Ramsey, B. D., Rankin, J., Roberts, O. J., Romani, R. W., Sgro, C., Slane, P., Spandre, G., Swartz, D. A., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy IC 4329A. The Imaging X-ray Polarimetry Explorer (IXPE) observed the source for ~500 ks, supported by XMM-Newton (~60 ks) and NuSTAR (~80 ks) exposures. We detect polarisation in the 2-8 keV band with 2.97 sigma confidence. We report a polarisation degree of $3.3\pm1.1$ per cent and a polarisation angle of $78\pm10$ degrees (errors are 1 sigma confidence). The X-ray polarisation is consistent with being aligned with the radio jet, albeit partially due to large uncertainties on the radio position angle. We jointly fit the spectra from the three observatories to constrain the presence of a relativistic reflection component. From this, we obtain constraints on the inclination angle to the inner disc (< 39 degrees at 99 per cent confidence) and the disc inner radius (< 11 gravitational radii at 99 per cent confidence), although we note that modelling systematics in practice add to the quoted statistical error. Our spectro-polarimetric modelling indicates that the 2-8 keV polarisation is consistent with being dominated by emission directly observed from the X-ray corona, but the polarisation of the reflection component is completely unconstrained. Our constraints on viewer inclination and polarisation degree tentatively favour more asymmetric, possibly out-flowing, coronal geometries that produce more highly polarised emission, but the coronal geometry is unconstrained at the 3 sigma level., Comment: Accepted for publication in MNRAS, 13 pages, 9 figures
Published: 2023

57. The geometry of the hot corona in MCG-05-23-16 constrained by X-ray polarimetry

Author: Tagliacozzo, D., Marinucci, A., Ursini, F., Matt, G., Bianchi, S., Baldini, L., Barnouin, T., Rodriguez, N. Cavero, De Rosa, A., Di Gesu, L., Dovciak, M., Harper, D., Ingram, A., Karas, V., Kim, D. E., Krawczynski, H., Madejski, G., Marin, F., Middei, R., Marshall, H. L., Muleri, F., Panagiotou, C., Petrucci, P. O., Podgorny, J., Poutanen, J., Puccetti, S., Soffitta, P., Tombesi, F., Veledina, A., Zhang, W., Agudo, I., Antonelli, L. A., Bachetti, M., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Chen, C. T., Ciprini, S., Costa, E., Del Monte, E., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Ehlert, S. R., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., Garcia, J. A., Gunji, S., Heyl, J., Iwakiri, W., Jorstad, S. G., Kaaret, P., Kislat, F., Kitaguchi, T., Kolodziejczak, J. J., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marscher, A. P., Massaro, F., Mitsuishi, I., Mizuno, T., Negro, M., Ng, C. Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Rollins, M. Pesce, Pilia, M., Possenti, A., Ramsey, B. D., Rankin, J., Ratheesh, A., Roberts, O. J., Romani, R. W., Sgrò, C., Slane, P., Spandre, G., Swartz, D. A., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the second observation of the radio-quiet active galactic nucleus (AGN) MCG-05-23-16 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation started on 2022 November 6 for a net observing time of 640 ks, and was partly simultaneous with NuSTAR (86 ks). After combining these data with those obtained in the first IXPE pointing on May 2022 (simultaneous with XMM-Newton and NuSTAR) we find a 2-8 keV polarization degree $\Pi$ = 1.6 $\pm$ 0.7 (at 68 per cent confidence level), which corresponds to an upper limit $\Pi$ = 3.2 per cent (at 99 per cent confidence level). We then compare the polarization results with Monte Carlo simulations obtained with the MONK code, with which different coronal geometries have been explored (spherical lamppost, conical, slab and wedge). Furthermore, the allowed range of inclination angles is found for each geometry. If the best fit inclination value from a spectroscopic analysis is considered, a cone-shaped corona along the disc axis is disfavoured., Comment: 9 pages, 8 figures, 3 table. Submitted to MNRAS
Published: 2023

58. The First X-ray Polarization Observation of the Black Hole X-ray Binary 4U 1630-47 in the Steep Power Law State

Author: Cavero, Nicole Rodriguez, Marra, Lorenzo, Krawczynski, Henric, Dovčiak, Michal, Bianchi, Stefano, Steiner, James F., Svoboda, Jiri, Capitanio, Fiamma, Matt, Giorgio, Negro, Michela, Ingram, Adam, Veledina, Alexandra, Taverna, Roberto, Karas, Vladimir, Ursini, Francesco, Podgorný, Jakub, Ratheesh, Ajay, Suleimanov, Valery, Mikušincová, Romana, Zane, Silvia, Kaaret, Philip, Muleri, Fabio, Poutanen, Juri, Malacaria, Christian, Petrucci, Pierre-Olivier, Gau, Ephraim, Hu, Kun, Chun, Sohee, 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, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, García, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Ng, Chi-Yung, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Roberts, Oliver J., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Soffitta, Paolo, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Imaging X-ray Polarimetry Explorer (IXPE) observed the black hole X-ray binary 4U 1630-47 in the steep power law (or very high) state. The observations reveal a linear polarization degree of the 2-8 keV X-rays of 6.8 +/- 0.2 % at a position angle of 21{\deg}.3 +/- 0{\deg}.9 East of North (all errors at 1{\sigma} confidence level). Whereas the polarization degree increases with energy, the polarization angle stays constant within the accuracy of our measurements. We compare the polarization of the source in the steep power-law state with the previous IXPE measurement of the source in the high soft state. We find that even though the source flux and spectral shape are significantly different between the high soft state and the steep power-law state, their polarization signatures are similar. Assuming that the polarization of both the thermal and power-law emission components are constant over time, we estimate the power-law component polarization to be 6.8-7.0% and note that the polarization angle of the thermal and power-law components must be approximately aligned. We discuss the implications for the origin of the power-law component and the properties of the emitting plasma., Comment: 14 pages, 2 tables, 6 figures
Published: 2023

59. Joint machine learning and analytic track reconstruction for X-ray polarimetry with gas pixel detectors

Author: Cibrario, Nicoló, Negro, Michela, Moriakov, Nikita, Bonino, Raffaella, Baldini, Luca, Di Lalla, Niccoló, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Omodei, Nicola, Sgró, Carmelo, and Tugliani, Stefano
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Physics - Instrumentation and Detectors
Abstract: We present our study on the reconstruction of photoelectron tracks in gas pixel detectors used for astrophysical X-ray polarimetry. Our work aims to maximize the performance of convolutional neural networks (CNNs) to predict the impact point of incoming X-rays from the image of the photoelectron track. A very high precision in the reconstruction of the impact point position is achieved thanks to the introduction of an artificial sharpening process of the images. We find that providing the CNN-predicted impact point as input to the state-of-the-art analytic analysis improves the modulation factor ($\sim 1 \%$ at 3 keV and $\sim 6 \%$ at 6 keV) and naturally mitigates a subtle effect appearing in polarization measurements of bright extended sources known as "polarization leakage".
Published: 2023
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60. X-ray Polarization of the Black Hole X-ray Binary 4U 1630-47 Challenges Standard Thin Accretion Disk Scenario

Author: Ratheesh, Ajay, Dovčiak, Michal, Krawczynski, Henric, Podgorný, Jakub, Marra, Lorenzo, Veledina, Alexandra, Suleimanov, Valery, Cavero, Nicole Rodriguez, Steiner, James, Svoboda, Jiri, Marinucci, Andrea, Bianchi, Stefano, Negro, Michela, Matt, Giorgio, Tombesi, Francesco, Poutanen, Juri, Ingram, Adam, Taverna, Roberto, West, Andrew, Karas, Vladimir, Ursini, Francesco, Soffitta, Paolo, Capitanio, Fiamma, Viscolo, Domenico, Manfreda, Alberto, Muleri, Fabio, Parra, Maxime, Beheshtipour, Banafsheh, Chun, Sohee, Cibrario, Niccolò, Di Lalla, Niccolò, Fabiani, Sergio, Hu, Kun, Kaaret, Philip, Loktev, Vladislav, Mikušincová, Romana, Mizuno, Tsunefumi, Omodei, Nicola, Petrucci, Pierre-Olivier, Puccetti, Simonetta, Rankin, John, Zane, Silvia, Zhang, Sixuan, Agudo, Iván, Antonelli, Lucio, Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne, Bellazzini, Ronaldo, Bongiorno, Stephen, Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Ehlert, Steven, Enoto, Teruaki, Evangelista, Yuri, Ferrazzoli, Riccardo, Garcia, Javier, Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Marin, Frédéric, Marscher, Alan, Marshall, Herman, Massaro, Francesco, Mitsuishi, Ikuyuki, Ng, C. -Y., O'Dell, Stephen, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George, Peirson, Abel, Perri, Matteo, Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Ramsey, Brian, Roberts, Oliver, Romani, Roger, Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Swartz, Douglas, Tamagawa, Toru, Tavecchio, Fabrizio, Tawara, Yuzuru, Tennant, Allyn, Thomas, Nicholas, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin, Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Large energy-dependent X-ray polarization degree is detected by the Imaging X-ray Polarimetry Explorer ({IXPE}) in the high-soft emission state of the black hole X-ray binary 4U 1630--47. The highly significant detection (at $\approx50\sigma$ confidence level) of an unexpectedly high polarization, rising from $\sim6\%$ at $2$ keV to $\sim10\%$ at $8$ keV, cannot be easily reconciled with standard models of thin accretion discs. In this work we compare the predictions of different theoretical models with the {IXPE} data and conclude that the observed polarization properties are compatible with a scenario in which matter accretes onto the black hole through a thin disc, covered by a partially-ionized atmosphere flowing away at mildly relativistic velocities., Comment: Published in ApJ (https://doi.org/10.3847/1538-4357/ad226e)
Published: 2023
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61. X-ray polarization evidence for a 200 years-old flare of Sgr A$^*$

Author: Marin, Frédéric, Churazov, Eugene, Khabibullin, Ildar, Ferrazzoli, Riccardo, Di Gesu, Laura, Barnouin, Thibault, Di Marco, Alessandro, Middei, Riccardo, Vikhlinin, Alexey, Costa, Enrico, Soffitta, Paolo, Muleri, Fabio, Sunyaev, Rashid, Forman, William, Kraft, Ralph, Bianchi, Stefano, Donnarumma, Immacolata, Petrucci, Pierre-Olivier, Enoto, Teruaki, Agudo, Iván, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolò, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Lalla, Niccolò, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Evangelista, Yuri, Fabiani, Sergio, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Ingram, Adam, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, 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, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver J., 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., 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, Astrophysics - Astrophysics of Galaxies, J.2.3, J.2.9
Abstract: The center of the Milky Way Galaxy hosts a $\sim$4 million solar mass black hole (Sgr A$^*$) that is currently very quiescent with a luminosity many orders of magnitude below those of active galactic nuclei. Reflection of X-rays from Sgr A$^*$ by dense gas in the Galactic Center region offers a means to study its past flaring activity on times scales of hundreds and thousands of years. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A$^*$ are consistent with the reflection scenario. If this interpretation is correct, the reflected continuum emission should be polarized. Here we report observations of polarized X-ray emission in the direction of the Galactic center molecular clouds using the Imaging X-ray Polarimetry Explorer (IXPE). We measure a polarization degree of 31\% $\pm$ 11\%, and a polarization angle of $-$48$^\circ$ $\pm$ 11$^\circ$. The polarization angle is consistent with Sgr A$^*$ being the primary source of the emission, while the polarization degree implies that some 200 years ago the X-ray luminosity of Sgr A$^*$ was briefly comparable to a Seyfert galaxy., Comment: 24 pages, 5 figures, 4 tables, author's version of the paper accepted for publication in Nature
Published: 2023
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62. A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375

Author: Malacaria, Christian, Heyl, Jeremy, Doroshenko, Victor, Tsygankov, Sergey S., Poutanen, Juri, Forsblom, Sofia V., Capitanio, Fiamma, Di Marco, Alessandro, Du, Yujia, Ducci, Lorenzo, La Monaca, Fabio, Lutovinov, Alexander A., Marshall, Herman L., Mereminskiy, Ilya A., Molkov, Sergey V., Ng, Mason, Petrucci, Pierre-Olivier, Santangelo, Andrea, Shtykovsky, Andrey E., Suleimanov, Valery F., Agudo, Ivan, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolo, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolo, Donnarumma, Immacolata, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak1, Jeffery J., Krawczynski, Henric, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Marscher, Alan P., 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., Perri, Matteo, Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, 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, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Accreting X-ray pulsars (XRPs) are presumably ideal targets for polarization measurements, as their high magnetic field strength is expected to polarize the emission up to a polarization degree of ~80%. However, such expectations are being challenged by recent observations of XRPs with the Imaging X-ray Polarimeter Explorer (IXPE). Here we report on the results of yet another XRP, EXO 2030+375, observed with IXPE and contemporarily monitored with Insight-HXMT and SRG/ART-XC. In line with recent results obtained with IXPE for similar sources, analysis of the EXO 2030+375 data returns a low polarization degree of 0%-3% in the phase-averaged study and variation in the range 2%-7% in the phase-resolved study. Using the rotating vector model we constrain the geometry of the system and obtain a value for the magnetic obliquity of ~$60^{\circ}$. Considering also the estimated pulsar inclination of ~$130^{\circ}$, this indicates that the magnetic axis swings close to the observer line of sight. Our joint polarimetric, spectral and timing analysis hint to a complex accreting geometry where magnetic multipoles with asymmetric topology and gravitational light bending significantly affect the observed source behavior., Comment: A&A accepted. Proofs version
Published: 2023
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63. X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator?

Author: Mushtukov, A. A., Tsygankov, S. S., Poutanen, J., Doroshenko, V., Salganik, A., Costa, E., Di Marco, A., Heyl, J., La Monaca, F., Lutovinov, A. A., Mereminsky, I. A., Papitto, A., Semena, A. N., Shtykovsky, A. E., Suleimanov, V. F., Forsblom, S. V., González-Caniulef, D., Malacaria, C., Sunyaev, R. A., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bianchi, S., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Chen, C. -T., Ciprini, S., De Rosa, A., Del Monte, E., Di Gesu, L., Di Lalla, N., Donnarumma, I., Dovčiak, M., Ehlert, S. R., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., Garcia, J. A., Gunji, S., Hayashida, K., Iwakiri, W., Jorstad, S. G., Kaaret, P., Karas, V., Kislat, F., Kitaguchi, T., Kolodziejczak, J. J., Krawczynski, H., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marin, F., Marscher, A. P., Marshall, H. L., Massaro, F., Matt, G., Mitsuishi, I., Mizuno, T., Muleri, F., Negro, M., Ng, C. -Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Petrucci, P. -O., Pilia, M., Possenti, A., Puccetti, S., Ramsey, B. D., Rankin, J., Ratheesh, A., Roberts, O. J., Romani, R. W., Sgrò, C., Slane, P., Soffitta, P., Spandre, G., Swartz, D. A., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Tombesi, F., Trois, A., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: X Persei is a persistent low-luminosity X-ray pulsar of period of $\sim$835 s in a Be binary system. The field strength at the neutron star surface is not known precisely, but indirect signs indicate a magnetic field above $10^{13}$ G, which makes the object one of the most magnetized known X-ray pulsars. Here we present the results of observations X Persei performed with the Imaging X-ray Polarimetry Explorer (IXPE). The X-ray polarization signal was found to be strongly dependent on the spin phase of the pulsar. The energy-averaged polarization degree in 3-8 keV band varied from several to $\sim$20 per cent over the pulse with a positive correlation with the pulsed X-ray flux. The polarization angle shows significant variation and makes two complete revolutions during the pulse period resulting in nearly nil pulse-phase averaged polarization. Applying the rotating vector model to the IXPE data we obtain the estimates for the rotation axis inclination and its position angle on the sky as well as for the magnetic obliquity. The derived inclination is close to the orbital inclination reported earlier for X Persei. The polarimetric data imply a large angle between the rotation and magnetic dipole axes, which is similar to the result reported recently for the X-ray pulsar GRO J1008$-$57. After eliminating the effect of polarization angle rotation over the pulsar phase using the best-fitting rotating vector model, the strong dependence of the polarization degree with energy was discovered with its value increasing from 0% at $\sim$2 keV to 30% at 8 keV., Comment: 11 pages, 7 figures, submitted to MNRAS
Published: 2023
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64. Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow

Author: Lesage, S., Veres, P., Briggs, M. S., Goldstein, A., Kocevski, D., Burns, E., Wilson-Hodge, C. A., Bhat, P. N., Huppenkothen, D., Fryer, C. L., Hamburg, R., Racusin, J., Bissaldi, E., Cleveland, W. H., Dalessi, S., Fletcher, C., Giles, M. M., Hristov, B. A., Hui, C. M., Mailyan, B., Malacaria, C., Poolakkil, S., Roberts, O. J., von Kienlin, A., Wood, J., Ajello, M., Arimoto, M., Baldini, L., Ballet, J., Baring, M. G., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Blandford, R. D., Bonino, R., Bruel, P., Buson, S., Cameron, R. A., Caputo, R., Caraveo, P. A., Cavazzuti, E., Chiaro, G., Cibrario, N., Ciprini, S., Orestano, P. Cristarella, Crnogorcevic, M., Cuoco, A., Cutini, S., DAmmando, F., De Gaetano, S., Di Lalla, N., Di Venere, L., Dominguez, A., Fegan, S. J., Ferrara, E. C., Fleischhack, H., Fukazawa, Y., Funk, S., Fusco, P., Galanti, G., Gammaldi, V., Gargano, F., Gasbarra, C., Gasparrini, D., Germani, S., Giacchino, F., Giglietto, N., Gill, R., Giroletti, M., Granot, J., Green, D., Grenier, I. A., Guiriec, S., Gustafsson, M., Hays, E., Hewitt, J. W., Horan, D., Hou, X., Kuss, M., Latronico, L., Laviron, A., Lemoine-Goumard, M., Li, J., Liodakis, I., Longo, F., Loparco, F., Lorusso, L., Lovellette, M. N., Lubrano, P., Maldera, S., Manfreda, A., Marti-Devesa, G., Mazziotta, M. N., McEnery, J. E., Mereu, I., Meyer, M., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panzarini, G., Persic, M., Pesce-Rollins, M., Pillera, R., Piron, F., Poon, H., Porter, T. A., Principe, G., Raino, S., Rando, R., Rani, B., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Ryde, F., Sanchez-Conde, M., Parkinson, P. M. Saz, Scotton, L., Serini, D., Sgro, C., Sharma, V., Siskind, E. J., Spandre, G., Spinelli, P., Tajima, H., Torres, D. F., Valverde, J., Venters, T., Wadiasingh, Z., Wood, K., and Zaharijas, G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report the discovery of GRB 221009A, the highest flux gamma-ray burst ever observed by the Fermi Gamma-ray Burst Monitor (GBM). This GRB has continuous prompt emission lasting more than 600 seconds which smoothly transitions to afterglow visible in the GBM energy range (8 keV--40 MeV), and total energetics higher than any other burst in the GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the GBM trigger time (t0; 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of the thermal, photospheric emission of shock-breakout, with significant emission up to $\sim$15 MeV. We characterize the onset of external shock at t0+600 s and find evidence of a plateau region in the early-afterglow phase which transitions to a slope consistent with Swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the GBM sample and find that this GRB has the highest total isotropic-equivalent energy ($\textrm{E}_{\gamma,\textrm{iso}}=1.0\times10^{55}$ erg) and second highest isotropic-equivalent luminosity ($\textrm{L}_{\gamma,\textrm{iso}}=9.9\times10^{53}$ erg/s) based on redshift of z = 0.151. These extreme energetics are what allowed us to observe the continuously emitting central engine of GBM from the beginning of the prompt emission phase through the onset of early afterglow., Comment: 26 pages 7 figures - accepted for publication in ApJL
Published: 2023
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65. Uncovering the geometry of the hot X-ray corona in the Seyfert galaxy NGC4151 with IXPE

Author: Gianolli, V. E., Kim, D. E., Bianchi, S., Agís-González, B., Madejski, G., Marin, F., Marinucci, A., Matt, G., Middei, R., Petrucci, P-O., Soffitta, P., Tagliacozzo, D., Tombesi, F., Ursini, F., Barnouin, T., De Rosa, A., Di Gesu, L., Ingram, A., Loktev, V., Panagiotou, C., Podgorny, J., Poutanen, J., Puccetti, S., Ratheesh, A., Veledina, A., Zhang, W., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Chen, C. -T., Ciprini, S., Costa, E., Del Monte, E., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Dovčiak, M., Ehlert, S. R., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., García, J. A., Gunji, S., Heyl, J., Iwakiri, W., Jorstad, S. G., Kaaret, P., Karas, V., Kislat, F., Kitaguchi, T., Kolodziejczak, J. J., Krawczynski, H., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marscher, A. P., Marshall, H. L., Massaro, F., Mitsuishi, I., Mizuno, T., Muleri, F., Negro, M., Ng, C. -Y., ODell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Pilia, M., Possenti, A., Ramsey, B. D., Rankin, J., Roberts, O. J., Romani, R. W., Sgrò, C., Slane, P., Spandre, G., Swartz, D. A., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present an X-ray spectro-polarimetric analysis of the bright Seyfert galaxy NGC4151. The source has been observed with the Imaging X-ray Polarimetry Explorer (IXPE) for 700 ks, complemented with simultaneous XMM-Newton (50 ks) and NuSTAR (100 ks) pointings. A polarization degree ${\Pi} = 4.9 {\pm} 1.1 \%$ and angle ${\Psi}= 86{\deg} {\pm} 7{\deg}$ east of north ($68\%$ confidence level) are measured in the 2-8 keV energy range. The spectro-polarimetric analysis shows that the polarization could be entirely due to reflection. Given the low reflection flux in the IXPE band, this requires however a reflection with a very large ($> 38 \%$) polarization degree. Assuming more reasonable values, a polarization degree of the hot corona ranging from ${\sim}4$ to ${\sim}8\%$ is found. The observed polarization degree excludes a spherical lamppost geometry for the corona, suggesting instead a slab-like geometry, possibly a wedge, as determined via Monte Carlo simulations. This is further confirmed by the X-ray polarization angle, which coincides with the direction of the extended radio emission in this source, supposed to match the disc axis. NGC4151 is the first AGN with an X-ray polarization measure for the corona, illustrating the capabilities of X-ray polarimetry and IXPE in unveiling its geometry., Comment: 9 pages, 4 figures
Published: 2023
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66. Vela pulsar wind nebula x-rays are polarized to near the synchrotron limit

Author: Xie, Fei, Di Marco, Alessandro, La Monaca, Fabio, Liu, Kuan, Muleri, Fabio, Bucciantini, Niccolò, Romani, Roger W., Costa, Enrico, Rankin, John, Soffitta, Paolo, Bachetti, Matteo, Di Lalla, Niccolò, Fabiani, Sergio, Ferrazzoli, Riccardo, Gunji, Shuichi, Latronico, Luca, Negro, Michela, Omodei, Nicola, Pilia, Maura, Trois, Alessio, Watanabe, Eri, Agudo, Iván, Antonelli, Lucio A., Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Garcia, Javier A., Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Ratheesh, Ajay, Sgró, Carmelo, Slane, Patrick, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas E., Tombesi, Francesco, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, age 11 kyr) and located inside an extended structure called Vela X, itself inside the supernova remnant. Previous X-ray observations revealed two prominent arcs, bisected by a jet and counter jet. Radio maps have shown high linear polarization of 60 per cent in the outer regions of the nebula. Here we report X-ray observation of the inner part of the nebula, where polarization can exceed 60 per cent at the leading edge, which approaches the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field., Comment: 27 pages, 8 figures, 4 tables, author's version of the paper accepted for publication in Nature
Published: 2023
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67. The first X-ray polarimetric observation of the black hole binary LMC X-1

Author: Podgorny, Jakub, Marra, Lorenzo, Muleri, Fabio, Cavero, Nicole Rodriguez, Ratheesh, Ajay, Dovciak, Michal, Mikusincova, Romana, Brigitte, Maimouna, Steiner, James F., Veledina, Alexandra, Bianchi, Stefano, Krawczynski, Henric, Svoboda, Jiri, Kaaret, Philip, Matt, Giorgio, Garcia, Javier A., Petrucci, Pierre-Olivier, Lutovinov, Alexander A., Semena, Andrey N., Di Marco, Alessandro, Negro, Michela, Weisskopf, Martin C., Ingram, Adam, Poutanen, Juri, Beheshtipour, Banfsheh, Chun, Sohee, Hu, Kun, Mizuno, Tsunefumi, Sixuan, Zhang, Tombesi, Francesco, Zane, Silvia, Agudo, Ivan, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, 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, Di Lalla, Niccolo, 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., La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Massaro, Francesco, Mitsuishi, Ikuyuki, Ng, Chi-Yung, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Roberts, Oliver J., Romani, Roger W., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Doug A., Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Vink, Jacco, Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on an X-ray polarimetric observation of the high-mass X-ray binary LMC X-1 in the high/soft state, obtained by the Imaging X-ray Polarimetry Explorer (IXPE) in October 2022. The measured polarization is below the minimum detectable polarization of 1.1 per cent (at the 99 per cent confidence level). Simultaneously, the source was observed with the NICER, NuSTAR and SRG/ART-XC instruments, which enabled spectral decomposition into a dominant thermal component and a Comptonized one. The low 2-8 keV polarization of the source did not allow for strong constraints on the black-hole spin and inclination of the accretion disc. However, if the orbital inclination of about 36 degrees is assumed, then the upper limit is consistent with predictions for pure thermal emission from geometrically thin and optically thick discs. Assuming the polarization degree of the Comptonization component to be 0, 4, or 10 per cent, and oriented perpendicular to the polarization of the disc emission (in turn assumed to be perpendicular to the large scale ionization cone orientation detected in the optical band), an upper limit to the polarization of the disc emission of 1.0, 0.9 or 0.9 per cent, respectively, is found (at the 99 per cent confidence level)., Comment: 12 pages, 9 figures, 4 tables. Accepted for publication in MNRAS
Published: 2023

68. Equalizing the Pixel Response of the Imaging Photoelectric Polarimeter On-Board the IXPE Mission

Author: Rankin, John, Muleri, Fabio, Di Marco, Alessandro, Fabiani, Sergio, La Monaca, Fabio, Soffitta, Paolo, Bachetti, Matteo, Baldini, Luca, Costa, Enrico, Di Lalla, Niccolò, Manfreda, Alberto, O'Dell, Stephen L., Perri, Matteo, Puccetti, Simonetta, Ramsey, Brian D., Sgrò, Carmelo, Tennant, Allyn F., Tobia, Antonino, Trois, Alessio, Weisskopf, Martin C., and Xie, Fei
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract: The Gas Pixel Detector is a gas detector, sensitive to the polarization of X-rays, currently flying on-board IXPE - the first observatory dedicated to X-ray polarimetry. It detects X-rays and their polarization by imaging the ionization tracks generated by photoelectrons absorbed in the sensitive volume, and then reconstructing the initial direction of the photoelectrons. The primary ionization charge is multiplied and ultimately collected on a finely-pixellated ASIC specifically developed for X-ray polarimetry. The signal of individual pixels is processed independently and gain variations can be substantial, of the order of 20%. Such variations need to be equalized to correctly reconstruct the track shape, and therefore its polarization direction. The method to do such equalization is presented here and is based on the comparison between the mean charge of a pixel with respect to the other pixels for equivalent events. The method is shown to finely equalize the response of the detectors on board IXPE, allowing a better track reconstruction and energy resolution, and can in principle be applied to any imaging detector based on tracks., Comment: Accepted for publication in The Astronomical Journal. 10 pages, 19 figures
Published: 2023
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69. IXPE observations of the quintessential wind-accreting X-ray pulsar Vela X-1

Author: Forsblom, Sofia V., Poutanen, Juri, Tsygankov, Sergey S., Bachetti, Matteo, Di Marco, Alessandro, Doroshenko, Victor, Heyl, Jeremy, La Monaca, Fabio, Malacaria, Christian, Marshall, Herman L., Muleri, Fabio, Mushtukov, Alexander A., Pilia, Maura, Rogantini, Daniele, Suleimanov, Valery F., Taverna, Roberto, Xi, Fei, Agudo, Iván, Antonelli, Lucio A., 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, Donnarumma, Immacolata, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Matt, Giorgio, 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, Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Sunyaev, Rashid A., Swartz, Doug, Tamagawa, Toru, Tavecchio, Fabrizio, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer (IXPE). Vela X-1 is considered to be the archetypal example of a wind-accreting high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectro-polarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3$\pm$0.4% at the polarization angle (PA) of -47.3$\pm$5.4 deg. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6-10%, and a 90 deg difference in the PA compared to the data in the 2-3 keV range. The phase-resolved spectro-polarimetric analysis finds a PD in the range 0-9% with the PA varying between -80 and 40 deg., Comment: 12 pages, 7 figures, ApJ Letters, submitted
Published: 2023
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70. 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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71. Atmospheric muons measured with the KM3NeT detectors in comparison with updated numeric predictions

Author: KM3NeT Collaboration, S. Aiello, A. Albert, M. Alshamsi, S. Alves Garre, A. Ambrosone, F. Ameli, M. Andre, E. Androutsou, M. Anguita, L. Aphecetche, M. Ardid, S. Ardid, A. Arsenic, H. Atmani, J. Aublin, F. Badaracco, L. Bailly-Salins, Z. Bardačová, B. Baret, A. Bariego-Quintana, S. Basegmez du Pree, Y. Becherini, M. Bendahman, F. Benfenati, M. Benhassi, D. M. Benoit, E. Berbee, V. Bertin, S. Biagi, M. Boettcher, D. Bonanno, J. Boumaaza, M. Bouta, M. Bouwhuis, C. Bozza, R. M. Bozza, H. Brânzaş, F. Bretaudeau, M. Breuhaus, R. Bruijn, J. Brunner, R. Bruno, E. Buis, R. Buompane, J. Busto, B. Caiffi, D. Calvo, S. Campion, A. Capone, F. Carenini, V. Carretero, T. Cartraud, P. Castaldi, V. Cecchini, S. Celli, L. Cerisy, M. Chabab, M. Chadolias, A. Chen, S. Cherubini, T. Chiarusi, M. Circella, R. Cocimano, J. A. B. Coelho, A. Coleiro, A. Condorelli, R. Coniglione, P. Coyle, A. Creusot, G. Cuttone, R. Dallier, Y. Darras, A. De Benedittis, B. De Martino, V. Decoene, R. Del Burgo, I. Del Rosso, L. S. Di Mauro, I. Di Palma, A. F. Díaz, C. Diaz, D. Diego-Tortosa, C. Distefano, A. Domi, C. Donzaud, D. Dornic, M. Dörr, E. Drakopoulou, D. Drouhin, J.-G. Ducoin, R. Dvornický, T. Eberl, E. Eckerová, A. Eddymaoui, T. van Eeden, M. Eff, D. van Eijk, I. El Bojaddaini, S. El Hedri, A. Enzenhöfer, G. Ferrara, M. D. Filipović, F. Filippini, D. Franciotti, L. A. Fusco, S. Gagliardini, T. Gal, J. García Méndez, A. Garcia Soto, C. Gatius Oliver, N. Geißelbrecht, H. Ghaddari, L. Gialanella, B. K. Gibson, E. Giorgio, I. Goos, P. Goswami, S. R. Gozzini, R. Gracia, K. Graf, C. Guidi, B. Guillon, M. Gutiérrez, C. Haack, H. van Haren, A. Heijboer, A. Hekalo, L. Hennig, J. J. Hernández-Rey, W. Idrissi Ibnsalih, G. Illuminati, D. Joly, M. de Jong, P. de Jong, B. J. Jung, P. Kalaczyński, O. Kalekin, U. F. Katz, A. Khatun, G. Kistauri, C. Kopper, A. Kouchner, V. Kueviakoe, V. Kulikovskiy, R. Kvatadze, M. Labalme, R. Lahmann, G. Larosa, C. Lastoria, A. Lazo, S. Le Stum, G. Lehaut, E. Leonora, N. Lessing, G. Levi, F. Longhitano, F. Magnani, J. Majumdar, L. Malerba, F. Mamedov, J. Mańczak, A. Manfreda, M. Marconi, A. Margiotta, A. Marinelli, C. Markou, L. Martin, F. Marzaioli, M. Mastrodicasa, S. Mastroianni, S. Miccichè, G. Miele, P. Migliozzi, E. Migneco, M. L. Mitsou, C. M. Mollo, L. Morales-Gallegos, G. Moretti, A. Moussa, I. Mozun Mateo, R. Muller, M. R. Musone, M. Musumeci, S. Navas, A. Nayerhoda, C. A. Nicolau, B. Nkosi, B. Ó. Fearraigh, V. Oliviero, A. Orlando, E. Oukacha, D. Paesani, J. Palacios González, G. Papalashvili, V. Parisi, E. J. Pastor Gomez, A. M. Păun, G. E. Păvălaş, I. Pelegris, S. Peña Martínez, M. Perrin-Terrin, J. Perronnel, V. Pestel, R. Pestes, P. Piattelli, C. Poirè, V. Popa, T. Pradier, J. Prado, S. Pulvirenti, C. A. Quiroz-Rangel, U. Rahaman, N. Randazzo, S. Razzaque, I. C. Rea, D. Real, G. Riccobene, J. Robinson, A. Romanov, A. Šaina, F. Salesa Greus, D. F. E. Samtleben, A. Sánchez Losa, S. Sanfilippo, M. Sanguineti, C. Santonastaso, D. Santonocito, P. Sapienza, J. Schnabel, J. Schumann, H. M. Schutte, J. Seneca, N. Sennan, B. Setter, I. Sgura, R. Shanidze, A. Sharma, Y. Shitov, F. Šimkovic, A. Simonelli, A. Sinopoulou, M. V. Smirnov, B. Spisso, M. Spurio, D. Stavropoulos, I. Štekl, M. Taiuti, Y. Tayalati, H. Thiersen, I. Tosta e Melo, E. Tragia, B. Trocmé, V. Tsourapis, A. Tudorache, E. Tzamariudaki, A. Vacheret, A. Valer Melchor, V. Valsecchi, V. Van Elewyck, G. Vannoye, G. Vasileiadis, F. Vazquez de Sola, A. Veutro, S. Viola, D. Vivolo, J. Wilms, E. de Wolf, H. Yepes-Ramirez, I. Yvon, G. Zarpapis, S. Zavatarelli, A. Zegarelli, D. Zito, J. D. Zornoza, J. Zúñiga, and N. Zywucka
Subjects: Astrophysics, QB460-466, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: Abstract The measurement of the flux of muons produced in cosmic ray air showers is essential for the study of primary cosmic rays. Such measurements are important in extensive air shower detectors to assess the energy spectrum and the chemical composition of the cosmic ray flux, complementary to the information provided by fluorescence detectors. Detailed simulations of the cosmic ray air showers are carried out, using codes such as CORSIKA, to estimate the muon flux at sea level. These simulations are based on the choice of hadronic interaction models, for which improvements have been implemented in the post-LHC era. In this work, a deficit in simulations that use state-of-the-art QCD models with respect to the measurement deep underwater with the KM3NeT neutrino detectors is reported. The KM3NeT/ARCA and KM3NeT/ORCA neutrino telescopes are sensitive to TeV muons originating mostly from primary cosmic rays with energies around 10 TeV. The predictions of state-of-the-art QCD models show that the deficit with respect to the data is constant in zenith angle; no dependency on the water overburden is observed. The observed deficit at a depth of several kilometres is compatible with the deficit seen in the comparison of the simulations and measurements at sea level.
Published: 2024
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72. Atmospheric muons measured with the KM3NeT detectors in comparison with updated numeric predictions

Author: Aiello, S., Albert, A., Alshamsi, M., Alves Garre, S., Ambrosone, A., Ameli, F., Andre, M., Androutsou, E., Anguita, M., Aphecetche, L., Ardid, M., Ardid, S., Arsenic, A., Atmani, H., Aublin, J., Badaracco, F., Bailly-Salins, L., Bardačová, Z., Baret, B., Bariego-Quintana, A., Pree, S. Basegmez du, Becherini, Y., Bendahman, M., Benfenati, F., Benhassi, M., Benoit, D. M., Berbee, E., Bertin, V., Biagi, S., Boettcher, M., Bonanno, D., Boumaaza, J., Bouta, M., Bouwhuis, M., Bozza, C., Bozza, R. M., Brânzaş, H., Bretaudeau, F., Breuhaus, M., Bruijn, R., Brunner, J., Bruno, R., Buis, E., Buompane, R., Busto, J., Caiffi, B., Calvo, D., Campion, S., Capone, A., Carenini, F., Carretero, V., Cartraud, T., Castaldi, P., Cecchini, V., Celli, S., Cerisy, L., Chabab, M., Chadolias, M., Chen, A., Cherubini, S., Chiarusi, T., Circella, M., Cocimano, R., Coelho, J. A. B., Coleiro, A., Condorelli, A., Coniglione, R., Coyle, P., Creusot, A., Cuttone, G., Dallier, R., Darras, Y., De Benedittis, A., De Martino, B., Decoene, V., Del Burgo, R., Del Rosso, I., Mauro, L. S. Di, Di Palma, I., Díaz, A. F., Diaz, C., Diego-Tortosa, D., Distefano, C., Domi, A., Donzaud, C., Dornic, D., Dörr, M., Drakopoulou, E., Drouhin, D., Ducoin, J.-G., Dvornický, R., Eberl, T., Eckerová, E., Eddymaoui, A., van Eeden, T., Eff, M., van Eijk, D., El Bojaddaini, I., El Hedri, S., Enzenhöfer, A., Ferrara, G., Filipović, M. D., Filippini, F., Franciotti, D., Fusco, L. A., Gagliardini, S., Gal, T., Méndez, J. García, Soto, A. Garcia, Oliver, C. Gatius, Geißelbrecht, N., Ghaddari, H., Gialanella, L., Gibson, B. K., Giorgio, E., Goos, I., Goswami, P., Gozzini, S. R., Gracia, R., Graf, K., Guidi, C., Guillon, B., Gutiérrez, M., Haack, C., van Haren, H., Heijboer, A., Hekalo, A., Hennig, L., Hernández-Rey, J. J., Ibnsalih, W. Idrissi, Illuminati, G., Joly, D., de Jong, M., de Jong, P., Jung, B. J., Kalaczyński, P., Kalekin, O., Katz, U. F., Khatun, A., Kistauri, G., Kopper, C., Kouchner, A., Kueviakoe, V., Kulikovskiy, V., Kvatadze, R., Labalme, M., Lahmann, R., Larosa, G., Lastoria, C., Lazo, A., Le Stum, S., Lehaut, G., Leonora, E., Lessing, N., Levi, G., Longhitano, F., Magnani, F., Majumdar, J., Malerba, L., Mamedov, F., Mańczak, J., Manfreda, A., Marconi, M., Margiotta, A., Marinelli, A., Markou, C., Martin, L., Marzaioli, F., Mastrodicasa, M., Mastroianni, S., Miccichè, S., Miele, G., Migliozzi, P., Migneco, E., Mitsou, M. L., Mollo, C. M., Morales-Gallegos, L., Moretti, G., Moussa, A., Mateo, I. Mozun, Muller, R., Musone, M. R., Musumeci, M., Navas, S., Nayerhoda, A., Nicolau, C. A., Nkosi, B., Fearraigh, B. Ó., Oliviero, V., Orlando, A., Oukacha, E., Paesani, D., González, J. Palacios, Papalashvili, G., Parisi, V., Pastor Gomez, E. J., Păun, A. M., Păvălaş, G. E., Pelegris, I., Peña Martínez, S., Perrin-Terrin, M., Perronnel, J., Pestel, V., Pestes, R., Piattelli, P., Poirè, C., Popa, V., Pradier, T., Prado, J., Pulvirenti, S., Quiroz-Rangel, C. A., Rahaman, U., Randazzo, N., Razzaque, S., Rea, I. C., Real, D., Riccobene, G., Robinson, J., Romanov, A., Šaina, A., Greus, F. Salesa, Samtleben, D. F. E., Losa, A. Sánchez, Sanfilippo, S., Sanguineti, M., Santonastaso, C., Santonocito, D., Sapienza, P., Schnabel, J., Schumann, J., Schutte, H. M., Seneca, J., Sennan, N., Setter, B., Sgura, I., Shanidze, R., Sharma, A., Shitov, Y., Šimkovic, F., Simonelli, A., Sinopoulou, A., Smirnov, M. V., Spisso, B., Spurio, M., Stavropoulos, D., Štekl, I., Taiuti, M., Tayalati, Y., Thiersen, H., Melo, I. Tosta e, Tragia, E., Trocmé, B., Tsourapis, V., Tudorache, A., Tzamariudaki, E., Vacheret, A., Melchor, A. Valer, Valsecchi, V., Elewyck, V. Van, Vannoye, G., Vasileiadis, G., de Sola, F. Vazquez, Veutro, A., Viola, S., Vivolo, D., Wilms, J., de Wolf, E., Yepes-Ramirez, H., Yvon, I., Zarpapis, G., Zavatarelli, S., Zegarelli, A., Zito, D., Zornoza, J. D., Zúñiga, J., and Zywucka, N.
Published: 2024
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73. X-ray pulsar GRO J1008$-$57 as an orthogonal rotator

Author: Tsygankov, Sergey S., Doroshenko, Victor, Mushtukov, Alexander A., Poutanen, Juri, Di Marco, Alessandro, Heyl, Jeremy, La Monaca, Fabio, Forsblom, Sofia, Malacaria, Christian, Marshall, Herman L., Suleimanov, Valery F., Svoboda, Jiri, Taverna, Roberto, Ursini, Francesco, Agudo, Iván, 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, Donnarumma, Immacolata, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., 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 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., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tamagawa, Toru, Tavecchio, Fabrizio, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: X-ray polarimetry is a unique way to probe the geometrical configuration of highly magnetized accreting neutron stars (X-ray pulsars). GRO J1008$-$57 is the first transient X-ray pulsar observed at two different flux levels by the Imaging X-ray Polarimetry Explorer (IXPE) during its outburst in November 2022. We find the polarization properties of GRO J1008$-$57 to be independent of its luminosity, with the polarization degree varying between nondetection and about 15% over the pulse phase. Fitting the phase-resolved spectro-polarimetric data with the rotating vector model allowed us to estimate the pulsar inclination (130 deg, which is in good agreement with the orbital inclination), the position angle (75 deg) of the pulsar spin axis, and the magnetic obliquity (74 deg). This makes GRO J1008$-$57 the first confidently identified nearly orthogonal rotator among X-ray pulsars. We discuss our results in the context of the neutron star atmosphere models and theories of the axis alignment of accreting pulsars., Comment: 11 pages, 7 figures, A&A, in press
Published: 2023
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74. Polarisation Leakage due to Errors in Track Reconstruction in Gas Pixel Detectors

Author: Bucciantini, N., Di Lalla, N., Romani, R. W. R., Silvestri, S., Negro, M., Baldini, L., Tennant, A. F., and Manfreda, A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract: X-ray polarimetry, based on Gas Pixel Detectors (GPDs), have reached a high level of maturity with the Imaging X-ray Polarimeter Explorer (IXPE) leading to the first ever spatially resolved polarimetric measures. However, being this a new technique, a few unexpected effect have emerged during in flight operations. In particular it was almost immediately found that on-board unpolarized calibration sources were showing radially polarized halos. The origin of this features was recognized in a correlation between the error in reconstructing the absorption point of the X-ray photon and the direction of its electric field vector. Here we present and discuss in detail this effect, showing that it is possible to provide a simple and robust mathematical formalism to handle it. We further show its role and relevance for the recent IXPE measures, and for the use of GPD-based techniques in general, and illustrate how to model it in the study of extended sources., Comment: 19 pages, 10 figures, to be published in A&A
Published: 2023
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75. A strong X-ray polarization signal from the magnetar 1RXS J170849.0-400910

Author: Zane, Silvia, Taverna, Roberto, Caniulef, Denis Gonzalez, Muleri, Fabio, Turolla, Roberto, Heyl, Jeremy, Uchiyama, Keisuke, Ng, Mason, Tamagawa, Toru, Caiazzo, Ilaria, Di Lalla, Niccolo', Marshall, Herman L., Bachetti, Matteo, La Monaca, Fabio, Gau, Ephraim, Di Marco, Alessandro, Baldini, Luca, Negro, Michela, Omodei, Nicola, Rankin, John, Matt, Giorgio, Pavlov, George G., Kitaguchi, Takao, Krawczynski, Henric, Kislat, Fabian, Kelly, Ruth, Agudo, Ivan, Antonelli, Lucio A., Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccolo', Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chieng Ting, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Donnarumma, Immacolata, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kolodziejczak, Jeffery J., Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Marscher, Alan P., Massaro, Francesco, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Ng, C. Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Peirson, Abel L., Perri, Matteo, Rollins, Melissa Pesce, Petrucci, Pierre Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Ratheesh, Ajay, Roberts, Oliver J., Romani, Roger W., Sgro', Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Swartz, Douglas A., Tavecchio, Fabrizio, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Magnetars are the most strongly magnetized neutron stars, and one of the most promising targets for X-ray polarimetric measurements. We present here the first Imaging X-ray Polarimetry Explorer (IXPE) observation of the magnetar 1RXS J170849.0-400910, jointly analysed with a new Swift observation and archival NICER data. The total (energy and phase integrated) emission in the 2-8 keV energy range is linerarly polarized, at a ~35% level. The phase-averaged polarization signal shows a marked increase with energy, ranging from ~20% at 2-3 keV up to ~80% at 6-8 keV, while the polarization angle remain constant. This indicates that radiation is mostly polarized in a single direction. The spectrum is well reproduced by a combination of either two thermal (blackbody) components or a blackbody and a power law. Both the polarization degree and angle also show a variation with the spin phase, and the former is almost anti-correlated with the source counts in the 2-8 keV and 2-4 keV bands. We discuss the possible implications and interpretations, based on a joint analysis of the spectral, polarization and pulsation properties of the source. A scenario in which the surface temperature is not homogeneous, with a hotter cap covered by a gaseous atmosphere and a warmer region in a condensed state, provides a satisfactory description of both the phase- and energy-dependent spectro-polarimetric data. The (comparatively) small size of the two emitting regions, required to explain the observed pulsations, does not allow to reach a robust conclusion about the presence of vacuum birefringence effects., Comment: 14 pages, 5 Figures, accepted for publication on ApJL
Published: 2023
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76. X-ray polarimetry reveals the magnetic field topology on sub-parsec scales in Tycho's supernova remnant

Author: Ferrazzoli, Riccardo, Slane, Patrick, Prokhorov, Dmitry, Zhou, Ping, Vink, Jacco, Bucciantini, Niccolò, Costa, Enrico, Di Lalla, Niccolò, Di Marco, Alessandro, Soffitta, Paolo, Weisskopf, Martin C., Asakura, Kazunori, Baldini, Luca, Heyl, Jeremy, Kaaret, Philip E., Marin, Frédéric, Mizuno, Tsunefumi, Ng, C. -Y., Pesce-Rollins, Melissa, Silvestri, Stefano, Sgrò, Carmelo, Swartz, Douglas A., Tamagawa, Toru, Yang, Yi-Jung, Agudo, Iván, Antonelli, Lucio A., Bachetti, Matteo, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Kislat, Fabian, Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Matt, Giorgio, Mitsuishi, Ikuyuki, Muleri, Fabio, Negro, Michela, O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Roberts, Oliver, Romani, Roger W., Spandre, Gloria, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey S., Turolla, Roberto, Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Supernova remnants are commonly considered to produce most of the Galactic cosmic rays via diffusive shock acceleration. However, many questions about the physical conditions at shock fronts, such as the magnetic-field morphology close to the particle acceleration sites, remain open. Here we report the detection of a localized polarization signal from some synchrotron X-ray emitting regions of Tycho's supernova remnant made by the Imaging X-ray Polarimetry Explorer. The derived polarization degree of the X-ray synchrotron emission is 9+/-2% averaged over the whole remnant, and 12+/-2% at the rim, higher than the 7-8% polarization value observed in the radio band. In the west region the polarization degree is 23+/-4%. The X-ray polarization degree in Tycho is higher than for Cassiopeia A, suggesting a more ordered magnetic-field or a larger maximum turbulence scale. The measured tangential polarization direction corresponds to a radial magnetic field, and is consistent with that observed in the radio band. These results are compatible with the expectation of turbulence produced by an anisotropic cascade of a radial magnetic-field near the shock, where we derive a magnetic-field amplification factor of 3.4+/-0.3. The fact that this value is significantly smaller than those expected from acceleration models is indicative of highly anisotropic magnetic-field turbulence, or that the emitting electrons either favor regions of lower turbulence, or accumulate close to where the magnetic-field orientation is preferentially radially oriented due to hydrodynamical instabilities., Comment: 31 pages, 7 figures, 3 tables. Accepted for publication in ApJ. Revised version
Published: 2023
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77. The Fermi-LAT Light Curve Repository

Author: Abdollahi, S., Ajello, M., Baldini, L., Ballet, J., Bastieri, D., Gonzalez, J. Becerra, Bellazzini, R., Berretta, A., Bissaldi, E., Bonino, R., Brill, A., Bruel, P., Burns, E., Buson, S., Cameron, A., Caputo, R., Caraveo, P. A., Cibrario, N., Ciprini, S., Orestano, P. Cristarella, Crnogorcevic, M., Cutini, S., D'Ammando, F., De Gaetano, S., Digel, S. W., Di Lalla, N., Di Venere, L., Domínguez, A., Ramazani, V. Fallah, Fegan, S. J., Ferrara, E. C., Fiori, A., Fleischhack, H., Franckowiak, A., Fukazawa, Y., Fusco, P., Gammaldi, V., Gargano, F., Garrappa, S., Gasbarra, C., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Green, D., Grenier, I. A., Guiriec, S., Gustafsson, M., Hays, E., Horan, D., Hou, X., Jóhannesson, G., Kerr, M., Kocevski, D., Kuss, M., Latronico, L., Li, J., Liodakis, I., Longo, F., Loparco, F., Lorusso, L., Lott, B., Lovellette, M. N., Lubrano, P., Maldera, S., Manfreda, A., Mart\'-Devesa, G., Mazziotta, M. N., Mereu, I., Meyer, M., Michelson, P. F., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Panzarini, G., Perkins, J. S., Persic, M., Pesce-Rollins, M., Pillera, R., Porter, T. A., Principe, G., Racusin, J. L., Rainò, S., Rando, R., Rani, B., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Sánchez-Conde, M., Parkinson, P. M. Saz, Scargle, Jeff, Scotton, L., Serini, D., Sgrò, C., Siskind, E. J., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Thompson, D. J., Torres, D. F., Valverde, J., Venters, T., Wadiasingh, Z., Wagner, S., and Wood, K.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Fermi Large Area Telescope (LAT) light curve repository (LCR) is a publicly available, continually updated library of gamma-ray light curves of variable Fermi-LAT sources generated over multiple timescales. The Fermi-LAT LCR aims to provide publication-quality light curves binned on timescales of 3 days, 7 days, and 30 days for 1525 sources deemed variable in the source catalog of the first 10 years of Fermi-LAT observations. The repository consists of light curves generated through full likelihood analyses that model the sources and the surrounding region, providing fluxes and photon indices for each time bin. The LCR is intended as a resource for the time-domain and multi-messenger communities by allowing users to quickly search LAT data to identify correlated variability and flaring emission episodes from gamma-ray sources. We describe the sample selection and analysis employed by the LCR and provide an overview of the associated data access portal., Comment: Accepted for publication in ApJ Supplement Series
Published: 2023
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78. The IXPE view of GRB 221009A

Author: Negro, Michela, Di Lalla, Niccoló, Omodei, Nicola, Veres, Péter, Silvestri, Stefano, Manfreda, Alberto, Burns, Eric, Baldini, Luca, Costa, Enrico, Ehlert, Steven R., Kennea, Jamie A., Liodakis, Ioannis, Marshall, Herman L., Mereghetti, Sandro, Middei, Riccardo, Muleri, Fabio, O'Dell, Stephen L., Roberts, Oliver J., Romani, Roger W., Sgró, Carmelo, Di Marco, Alessandro, Puccetti, Simonetta, Terashima, Masanobu, Tiengo, Andrea, Viscolo, Domenico, La Monaca, Fabio, Latronico, Luca, Matt, Giorgio, Perri, Matteo, Poutanen, Juri, Ratheesh, Ajay, Rogantini, Daniele, Slane, Patrick, Soffitta, Paolo, Lindfors, Elina, Nilsson, Kari, Kasikov, Anni, Marscher, Alan P., Tavecchio, Fabrizio, Gunji, Shuichi, Malacaria, Christian, Paggi, Alessandro, Yang, Yi-Jung, Zane, Silvia, Weisskopf, Martin C., Agudo, Iván, Antonelli, Lucio A., Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccol, Castellano, Simone, Cavazzuti, Elisabetta, Chen, Chien-Ting, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Donnarumma, Immacolata, Doroshenko, Victor, Dovciak, Michal, Enoto, Teruaki, Bachetti, Matteo, Bongiorno, Stephen D., Capitanio, Fiamma, Ciprini, Stefano, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Kaaret, Philip, Karas, Vladimir, Kislat, Fabian, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Maldera, Simone, Marin, Frédéric, Marinucci, Andrea, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Ng, C. -Y., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Pesce-Rollins, Melissa, Petrucci, Pierre-Olivier, Ramsey, Brian D., Rankin, John, Spandre, Gloria, Pilia, Maura, Possenti, Andrea, 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, Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the IXPE observation of GRB 221009A which includes upper limits on the linear polarization degree of both prompt and afterglow emission in the soft X-ray energy band. GRB 221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth on 2022 October 9 after travelling through the dust of the Milky Way. The Imaging X-ray Polarimetry Explorer (IXPE) pointed at GRB 221009A on October 11 to observe, for the first time, the 2-8 keV X-ray polarization of a GRB afterglow. We set an upper limit to the polarization degree of the afterglow emission of 13.8% at a 99% confidence level. This result provides constraints on the jet opening angle and the viewing angle of the GRB, or alternatively, other properties of the emission region. Additionally, IXPE captured halo-rings of dust-scattered photons which are echoes of the GRB prompt emission. The 99% confidence level upper limit to the prompt polarization degree depends on the background model assumption and it ranges between ~55% to ~82%. This single IXPE pointing provides both the first assessment of X-ray polarization of a GRB afterglow and the first GRB study with polarization observations of both the prompt and afterglow phases., Comment: Accepted by Astrophysical Journal Letters
Published: 2023
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79. Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

Author: Farinelli, R., Fabiani, S., Poutanen, J., Ursini, F., Ferrigno, C., Bianchi, S., Cocchi, M., Capitanio, F., De Rosa, A., Gnarini, A., Kislat, F., Matt, G., Mikusincova, R., Muleri, F., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Castellano, S., Cavazzuti, E., Ciprini, S., Costa, E., Del Monte, E., Di Gesu, L., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Dovčiak, M., Ehlert, S. R., Enoto, T., Evangelista, Y., Ferrazzoli, R., Garcia, J. A., Gunji, S., Hayashida, K., Heyl, J., Iwakiri, W., Jorstad, S. G., Karas, V., Kitaguchi, T., Kolodziejczak, J. J., Krawczynski, H., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marin, F., Marscher, A. P., Marshall, H. L., Mitsuishi, I., Mizuno, T., Ng, C. -Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Petrucci, P. O., Pilia, M., Possenti, A., Puccetti, S., Ramsey, B. D., Rankin, J., Ratheesh, A., Romani, R. W., Sgrò, C., Slane, P., Soffitta, P., Spandre, G., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Tombesi, F., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with $kT_{\rm in} \approx$ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature $kT_{\rm e} = 3$ keV and optical depth $\tau \approx 4$, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band $P=1.8 \pm 0.3$ per cent and polarization angle $\phi = 140^{\circ} \pm 4^{\circ}$, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree $P =4.0 \pm 0.7$ per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line., Comment: 10 pages, 7 figures, accepted for publication in MNRAS
Published: 2022
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80. Polarization properties of the weakly magnetized neutron star X-ray binary GS 1826-238 in the high soft state

Author: Capitanio, Fiamma, Fabiani, Sergio, Gnarini, Andrea, Ursini, Francesco, Ferrigno, Carlo, Matt, Giorgio, Poutanen, Juri, Cocchi, Massimo, Mikusincova, Romana, Farinelli, Ruben, Bianchi, Stefano, Kajava, Jari J. E., Muleri, Fabio, Sanchez-Fernandez, Celia, Soffitta, Paolo, Wu, Kinwah, Agudo, Ivan, Antonelli, Lucio A., Bachetti, Matteo, Baldini, Luca, Baumgartner, Wayne H., Bellazzini, Ronaldo, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Bucciantini, Niccoló, Castellano, Simone, Cavazzuti, Elisabetta, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolo, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Fréedèric, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Ng, C. -Y., O'Dell, Stephen L., Omodei, Nicola, Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, -Rollins, Melissa Pesce, Petrucci, Pierre-Olivier, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, 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 - Solar and Stellar Astrophysics
Abstract: The launch of the Imaging X-ray Polarimetry Explorer (IXPE) on 2021 December 9 has opened a new window in X-ray astronomy. We report here the results of the first IXPE observation of a weakly magnetized neutron star, GS 1826-238, performed on 2022 March 29-31 when the source was in a high soft state. An upper limit (99.73% confidence level) of 1.3% for the linear polarization degree is obtained over the IXPE 2-8 keV energy range. Coordinated INTEGRAL and NICER observations were carried out simultaneously with IXPE. The spectral parameters obtained from the fits to the broad-band spectrum were used as inputs for Monte Carlo simulations considering different possible geometries of the X-ray emitting region. Comparing the IXPE upper limit with these simulations, we can put constraints on the geometry and inclination angle of GS 1826-238., Comment: Accpted for publication in ApJ
Published: 2022
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81. Comparative analysis of the microbiome composition of artisanal cheeses produced in the Mediterranean area

Author: Valentina Indio, Ursula Gonzales-Barron, Chiara Oliveri, Alex Lucchi, Antonio Valero, Fouad Achemchem, Gerardo Manfreda, Federica Savini, Andrea Serraino, and Alessandra De Cesare
Subjects: Shotgun metagenomic, artisanal cheese, biological hazards, antimicrobial resistance, Mediterranean products, Food processing and manufacture, TP368-456
Abstract: In the PRIMA project ArtiSaneFood, the microbiological parameters of several artisanal cheeses produced in the Mediterranean area have been quantified. In this pilot study, we selected four of these artisanal cheese products from Italy, Portugal, Spain, and Morocco to investigate and compare their microbiomes in terms of taxonomy composition, presence of reads of foodborne pathogens, as well as virulence and antimicrobial resistance genes. Lactococcus, Streptococcus and Lactobacillus were the most represented genera in the Portuguese and Spanish cheeses, Streptococcus in the Italian cheese, and Enterococcus, Klebsiella, Escherichia, and Citrobacter in the Moroccan products. The correlation analysis indicated a negative association between the abundance of some lactic acid bacteria (i.e., Lactococcus, Lactobacillus, Streptococcus, and Leuconostoc) and foodborne pathogenic genera, like Escherichia and Salmonella. The analysis of pathogen abundance, virulence factors, and antimicrobial resistance genes showed a strong clusterization based on the cheese type, confirming that the presence of potential human health risk determinants was higher in the artisanal products derived from unpasteurized milk that underwent spontaneous fermentation.
Published: 2024
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82. Testing trends in gridded rainfall datasets at relevant hydrological scales: A comparative study with regional ground observations in Southern Italy

Author: Carmelo Cammalleri, Awais Naeem Sarwar, Angelo Avino, Gholamreza Nikravesh, Brunella Bonaccorso, Giuseppe Mendicino, Alfonso Senatore, and Salvatore Manfreda
Subjects: Annual and seasonal rainfall, Trends, Change points, E-OBS, ERA5, Physical geography, GB3-5030, Geology, QE1-996.5
Abstract: Study region: In this study, we compared the spatiotemporal evolution of rainfall trends in E-OBS and ERA5 to those detected using historical rainfall series recorded by ground-based networks in Southern Italy. In particular, the study is applied to the Campania, Basilicata, Apulia, Calabria and Sicily regions (84,000 km2 in total) on seasonal and annual scales. Study focus: Meteorological gridded datasets at large spatial scales are widely used in many hydroclimatic applications as they provide long and spatially homogeneous records. Regional trend analyses based on these data need to be treated with caution due to some potential limitations at relevant hydrological scales, such as the coarse spatial resolution and the spatio-temporal inhomogeneity of the underlying data. Gradual trends and abrupt change points were studied on rainfall data from 1979 to 2019. New hydrological insights for the region: Both gridded datasets capture the major trends in observed rainfall, with a predominance of positive values driven by changes in September-November. Overall, ERA5 returns flatter results compared to E-OBS, with the former comparing well with observations in Sicily and Apulia, while the latter is performing well in Campania and partially in Calabria and Basilicata. Most statistically significant trends are associated with discontinuities in the early 2000s, and this is well captured by both ground and gridded datasets. The general behavior in inter-annual variability trends in Southern Italy is captured by both datasets, with ERA5 also detecting regional patterns.
Published: 2024
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83. Balancing Accuracy and Efficiency for River Plastic Monitoring.

Author: Khim Cathleen Saddi, Domenico Miglino, Francesco Isgrò, Tim van Emmerik, and Salvatore Manfreda
Published: 2024
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84. Advancing Sustainable Water Management in Southern Italy Through Integrated Hydrological Modeling and Earth Observation.

Author: Vito Iacobellis, Andrea Gioia, Vincenzo Totaro, Margherita Lombardo, Aras Botan Izzaddin, Salvatore Manfreda, Ruodan Zhuang, Giuseppe Satalino, Anna Balenzano, Cinzia Albertini, Francesco Mattia, Francesco P. Lovergine, Davide Palmisano, Michele Rinaldi, Sergio Ruggieri, Pasquale Garofalo, Donato Impedovo, Nicoletta Noviello, Luigi Nardella, Michele Di Cataldo, Rocchina Guarini, Maria Virelli, Patrizia Sacco, and Deodato Tapete
Published: 2024
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85. Advancing Sustainable Water Management in Southern Italy Through Integrated Hydrological Modeling and Earth Observation

Author: Iacobellis, Vito, Gioia, Andrea, Totaro, Vincenzo, Lombardo, Margherita, Izzaddin, Aras Botan, Manfreda, Salvatore, Zhuang, Ruodan, Satalino, Giuseppe, Balenzano, Anna, Albertini, Cinzia, Mattia, Francesco, Lovergine, Francesco, Palmisano, Davide, Rinaldi, Michele, Ruggieri, Sergio, Garofalo, Pasquale, Impedovo, Donato, Noviello, Nicoletta, Nardella, Luigi, Di Cataldo, Michele, Guarini, Rocchina, Virelli, Maria, Sacco, Patrizia, Tapete, Deodato, Goos, Gerhard, Series Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Gervasi, Osvaldo, editor, Murgante, Beniamino, editor, Garau, Chiara, editor, Taniar, David, editor, C. Rocha, Ana Maria A., editor, and Faginas Lago, Maria Noelia, editor
Published: 2024
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86. Smart City as a Mix of Technology, Sustainability and Well-Being: A Myth or Reality?

Author: Manfreda, Anton, Mijač, Tea, Rannenberg, Kai, Editor-in-Chief, Soares Barbosa, Luís, Editorial Board Member, Carette, Jacques, Editorial Board Member, Tatnall, Arthur, Editorial Board Member, Neuhold, Erich J., Editorial Board Member, Stiller, Burkhard, Editorial Board Member, Stettner, Lukasz, Editorial Board Member, Pries-Heje, Jan, Editorial Board Member, Kreps, David, Editorial Board Member, Rettberg, Achim, Editorial Board Member, Furnell, Steven, Editorial Board Member, Mercier-Laurent, Eunika, Editorial Board Member, Winckler, Marco, Editorial Board Member, Malaka, Rainer, Editorial Board Member, Sharma, Sujeet K., editor, Dwivedi, Yogesh K., editor, Metri, Bhimaraya, editor, Lal, Banita, editor, and Elbanna, Amany, editor
Published: 2024
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87. 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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88. Mapping the circumnuclear regions of the Circinus galaxy with the Imaging X-ray Polarimetry Explorer

Author: Ursini, F., Marinucci, A., Matt, G., Bianchi, S., Marin, F., Marshall, H. L., Middei, R., Poutanen, J., Rogantini, D., De Rosa, A., Di Gesu, L., García, J. A., Ingram, A., Kim, D. E., Krawczynski, H., Puccetti, S., Soffitta, P., Svoboda, J., Tombesi, F., Weisskopf, M. C., Barnouin, T., Perri, M., Podgorny, J., Ratheesh, A., Zaino, A., Agudo, I., Antonelli, L. A., Bachetti, M., Baldini, L., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Ciprini, S., Costa, E., Del Monte, E., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Dovčiak, M., Ehlert, S. R., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., Gunji, S., Heyl, J., Iwakiri, W., Jorstad, S. G., Karas, V., Kitaguchi, T., Kolodziejczak, J. J., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marscher, A. P., Mitsuishi, I., Mizuno, T., Muleri, F., Ng, C. Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Pesce-Rollins, M., Petrucci, P. -O., Pilia, M., Possenti, A., Ramsey, B. D., Rankin, J., Romani, R. W., Sgrò, C., Slane, P., Spandre, G., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the Imaging X-ray Polarimetry Explorer (IXPE) observation of the closest and X-ray brightest Compton-thick active galactic nucleus (AGN), the Circinus galaxy. We find the source to be significantly polarized in the 2--6 keV band. From previous studies, the X-ray spectrum is known to be dominated by reflection components, both neutral (torus) and ionized (ionization cones). Our analysis indicates that the polarization degree is $28 \pm 7$ per cent (at 68 per cent confidence level) for the neutral reflector, with a polarization angle of $18{\deg} \pm 5{\deg}$, roughly perpendicular to the radio jet. The polarization of the ionized reflection is unconstrained. A comparison with Monte Carlo simulations of the polarization expected from the torus shows that the neutral reflector is consistent with being an equatorial torus with a half-opening angle of 45{\deg}-55{\deg}. This is the first X-ray polarization detection in a Seyfert galaxy, demonstrating the power of X-ray polarimetry in probing the geometry of the circumnuclear regions of AGNs, and confirming the basic predictions of standard Unification Models., Comment: 9 pages, accepted for publication in MNRAS, authors list updated
Published: 2022
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89. Observations of 4U 1626-67 with the Imaging X-ray Polarimetry Explorer

Author: Marshall, Herman L., Ng, Mason, Rogantini, Daniele, Heyl, Jeremy, Tsygankov, Sergey S., Poutanen, Juri, Costa, Enrico, Zane, Silvia, Malacaria, Christian, Agudo, Ivan, 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, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolo, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovvciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frederic, Marinucci, Andrea, Marscher, Alan P., Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Ng, C. -Y., ODell, 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, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgro, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicholas E., Tombesi, Francesco, Trois, Alessio, Turolla, Roberto, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, Schulz, Norbert S., and Chakrabarty, Deepto
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present measurements of the polarization of X-rays in the 2-8 keV band from the pulsar in the ultracompact low mass X-ray binary 4U1626-67 using data from the Imaging X-ray Polarimetry Explorer (IXPE). The 7.66 s pulsations were clearly detected throughout the IXPE observations as well as in the NICER soft X-ray observations, which we use as the basis for our timing analysis and to constrain the spectral shape over 0.4-10 keV energy band. Chandra HETGS high-resolution X-ray spectra were also obtained near the times of the IXPE observations for firm spectral modeling. We find an upper limit on the pulse-averaged linear polarization of <4% (at 95% confidence). Similarly, there was no significant detection of polarized flux in pulse phase intervals when subdividing the bandpass by energy. However, spectropolarimetric modeling over the full bandpass in pulse phase intervals provide a marginal detection of polarization of the power-law spectral component at the 4.8 +/- 2.3% level (90% confidence). We discuss the implications concerning the accretion geometry onto the pulsar, favoring two-component models of the pulsed emission., Comment: 19 pages, 7 figures, 7 tables; accepted for publication in the Astrophysical Journal
Published: 2022
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90. The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope -- Data Release 3

Author: collaboration, The Fermi-LAT, Ajello, Marco, Baldini, Luca, Ballet, Jean, Bastieri, Denis, Gonzalez, Josefa Becerra, Bellazzini, Ronaldo, Berretta, Alessandra, Bissaldi, Elisabetta, Bonino, Raffaella, Brill, Ari, Bruel, Philippe, Buson, Sara, Caputo, Regina, Caraveo, Patrizia, Cheung, Teddy, Chiaro, Graziano, Cibrario, Nicolo, Ciprini, Stefano, Crnogorcevic, Milena, Cutini, Sara, D'Ammando, Filippo, De Gaetano, Salvatore, Di Lalla, Niccolo, Di Venere, Leonardo, Dominguez, Alberto, Ramazani, Vandad Fallah, Ferrara, Elizabeth, Fiori, Alessio, Fukazawa, Yasushi, Funk, Stefan, Fusco, Piergiorgio, Gammaldi, Viviana, Gargano, Fabio, Garrappa, Simone, Gasparrini, Dario, Giglietto, Nico, Giordano, Francesco, Giroletti, Marcello, Green, David, Grenier, Isabelle, Guiriec, Sylvain, Horan, Deirdre, Hou, Xian, Kayanoki, Taishu, Kuss, Michael, Larsson, Stefan, Latronico, Luca, Lewis, Tiffany, Li, Jian, Liodakis, Ioannis, Longo, Francesco, Loparco, Francesco, Lott, Benoit, Lovellette, Michael, Lubrano, Pasquale, Madejski, Grzegorz, Maldera, Simone, Manfreda, Alberto, Marti-Devesa, Guillem, Mazziotta, Mario Nicola, Mereu, Isabella, Michelson, Peter, Mirabal, Nestor, Mitthumsiri, Warit, Mizuno, Tsunefumi, Monzani, Maria Elena, Morselli, Aldo, Moskalenko, Igor, Negro, Michela, Ojha, Roopesh, Orienti, Monica, Orlando, Elena, Ormes, Jonathan F., Pei, Zhiyuan, Pena-Herazo, Harold A., Persic, Massimo, Pesce-Rollins, Melissa, Petrosian, Vahe, Pillera, Roberta, Poon, Helen, Porter, Troy, Principe, Giacomo, Raino, Silvia, Rando, Riccardo, Rani, Bindu, Razzano, Massimiliano, Razzaque, Soebur, Reimer, Anita, Reimer, Olaf, Scargle, Jeff, Scotton, Lorenzo, Serini, Davide, Sgro, Carmelo, Siskind, Eric J., Spandre, Gloria, Spinelli, Paolo, Suson, Dan, Tajima, Hiro, Torres, Diego F., Valverde, Janeth, Yassin, Hend, and Zaharijas, Gabrijela
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi-Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of E>50 MeV gamma-ray data, where the spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The new reported AGNs include 587 blazar candidates and four radio galaxies. We describe the properties of the new sample and outline changes affecting the previously published one. We also introduce two new parameters in this release, namely the peak energy of the SED high-energy component and the corresponding flux. These parameters allow an assessment of the Compton dominance, the ratio of the Inverse-Compton to the synchrotron peak luminosities, without relying on X-ray data., Comment: 13 pages, 7 figures, accepted for publication in The Astrophysical Journal Supplement Series. Fits files are available at https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/ or alternatively at https://www.ssdc.asi.it/fermi4lac-DR3/table-4LAC-DR3-h.fits and https://www.ssdc.asi.it/fermi4lac-DR3/table-4LAC-DR3-l.fits
Published: 2022
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91. The X-ray Polarization View of Mrk~421 in an Average Flux State as Observed by the Imaging X-ray Polarimetry Explorer

Author: Di Gesu, Laura, Donnarumma, Immacolata, Tavecchio, Fabrizio, Agudo, Ivan, Barnounin, Thibault, Cibrario, Nicolò, Di Lalla, Niccolò, Di Marco, Alessandro, Escudero, Juan, Errando, Manel, Jorstad, Svetlana G., Kim, Dawoon, Kouch, Pouya M., Lindfors, Elina, Liodakis, Ioannis, Madejski, Grzegorz, Marshall, Herman L., Marscher, Alan P., Middei, Riccardo, Muleri, Fabio, Myserlis, Ioannis, Negro, Michela, Omodei, Nicola, Pacciani, Luigi, Paggi, Alessandro, Perri, Matteo, Puccetti, Simonetta, 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, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, 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, 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, Mizuno, Tsunefumi, 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, Poutanen, Juri, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas 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
Abstract: Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multi-wavelength polarization properties of blazars. The recent launch of the Imaging X-ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2-8 keV) to probe the properties of the jet synchrotron emission in high-frequency-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree $\Pi_{\rm x}=15\pm$2\% and electric-vector position angle $\Psi_{\rm x}=35^\circ\pm4^\circ$) from the jet of the HSP Mrk~421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of $\Pi_{\rm x}$ compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock as the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field., Comment: accepted for ApJ Letters
Published: 2022
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92. Polarized Blazar X-rays imply particle acceleration in shocks

Author: Liodakis, Ioannis, Marscher, Alan P., Agudo, Iván, Berdyugin, Andrei V., Bernardos, Maria I., Bonnoli, Giacomo, Borman, George A., Casadio, Carolina, Casanova, Víctor, Cavazzuti, Elisabetta, Cavero, Nicole Rodriguez, Di Gesu, Laura, Di Lalla, Niccoló, Donnarumma, Immacolata, Ehlert, Steven R., Errando, Manel, Escudero, Juan, García-Comas, Maya, Agís-González, Beatriz, Husillos, César, Jormanainen, Jenni, Jorstad, Svetlana G., Kagitani, Masato, Kopatskaya, Evgenia N., Kravtsov, Vadim, Krawczynski, Henric, Lindfors, Elina, Larionova, Elena G., Madejski, Grzegorz M., Marin, Frédéric, Marchini, Alessandro, Marshall, Herman L., Morozova, Daria A., Massaro, Francesco, Masiero, Joseph R., Mawet, Dimitri, Middei, Riccardo, Millar-Blanchaer, Maxwell A., Myserlis, Ioannis, Negro, Michela, Nilsson, Kari, O'Dell, Stephen L., Omodei, Nicola, Pacciani, Luigi, Paggi, Alessandro, Panopoulou, Georgia V., Peirson, Abel L., Perri, Matteo, Petrucci, Pierre-Olivier, Poutanen, Juri, Puccetti, Simonetta, Romani, Roger W., Sakanoi, Takeshi, Savchenko, Sergey S., Sota, Alfredo, Tavecchio, Fabrizio, Tinyanont, Samaporn, Vasilyev, Andrey A., Weaver, Zachary R., Zhovtan, Alexey V., 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., La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Marinucci, Andrea, Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, Muleri, Fabio, Ng, Stephen C. -Y., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Sgró, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas 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
Abstract: Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to $\sim 1$ TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization - the only range available until now - probe extended regions of the jet containing particles that left the acceleration site days to years earlier (Jorstad et al., 2005; Marin et al., 2018; Blinov et al., 2021), and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian~501 (Mrk~501). We measure an X-ray linear polarization degree $\Pi_X \sim10\%$, a factor of $\sim2$ higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration, and also implies that the plasma becomes increasingly turbulent with distance from the shock., Comment: 34 pages, 4 figures, 4 tables
Published: 2022
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93. The X-ray polarimetry view of the accreting pulsar Cen X-3

Author: Tsygankov, Sergey S., Doroshenko, Victor, Poutanen, Juri, Heyl, Jeremy, Mushtukov, Alexander A., Caiazzo, Ilaria, Di Marco, Alessandro, Forsblom, Sofia V., González-Caniulef, Denis, Klawin, Moritz, La Monaca, Fabio, Malacaria, Christian, Marshall, Herman L., Muleri, Fabio, Ng, Mason, Suleimanov, Valery F., Sunyaev, Rashid A., Turolla, Roberto, Agudo, Iván, 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, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Lalla, Niccolò, Donnarumma, Immacolata, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Ferrazzoli, Riccardo, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Matt, Giorgio, Mitsuishi, Ikuyuki, Mizuno, Tsunefumi, 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, Puccetti, Simonetta, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas E., Tombesi, Francesco, Trois, Alessio, Vink, Jacco, Weisskopf, Martin C., Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Cen X-3 is the first X-ray pulsar discovered 50 years ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ~20 in flux. In the low-luminosity state no significant polarization was found either in pulse phase-averaged (with the 3$\sigma$ upper limit of 12%) or phase-resolved data (the 3$\sigma$ upper limits are 20-30%). In the bright state the polarization degree of 5.8$\pm$0.3% and polarization angle of $49.6\deg\pm1.5\deg$ with significance of about 20$\sigma$ was measured from the spectro-polarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anti-correlation between the flux and the polarization degree as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49$\deg$ and a magnetic obliquity of 17$\deg$. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain., Comment: Submitted to ApJL. 18 pages, 12 figures
Published: 2022
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94. XPOL-III: a New-Generation VLSI CMOS ASIC for High-Throughput X-ray Polarimetry

Author: Minuti, M., Baldini, L., Bellazzini, R., Brez, A., Ceccanti, M., Krummenacher, F., Latronico, L., Lucchesi, L., Manfreda, A., Orsini, L., Pinchera, M., Profeti, A., Sgr`o, C., and Spandre, G.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: While the successful launch and operation in space of the Gas Pixel Detectors onboard the PolarLight cubesat and the Imaging X-ray Polarimetry Explorer demonstrate the viability and the technical soundness of this class of detectors for astronomical X-ray polarimetry, it is clear that the current state of the art is not ready to meet the challenges of the next generation of experiments, such as the enhanced X-ray Timing and Polarimetry mission, designed to allow for a significantly larger data throughput. In this paper we describe the design and test of a new custom, self-triggering readout ASIC, dubbed XPOL-III, specifically conceived to address and overcome these limitations. While building upon the overall architecture of the previous generations, the new chip improves over its predecessors in several, different key areas: the sensitivity of the trigger electronics, the flexibility in the definition of the readout window, as well as the maximum speed for the serial event readout. These design improvements, when combined, allow for almost an order of magnitude smaller dead time per event with no measurable degradation of the polarimetric, spectral, imaging or timing capability of the detector, providing a good match for the next generation of X-ray missions., Comment: accepted for publication at Nuclear Inst. and Methods in Physics Research Section A
Published: 2022
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95. Polarization constraints on the X-ray corona in Seyfert Galaxies: MCG-05-23-16

Author: Marinucci, A., Muleri, F., Dovčiak, M., Bianchi, S., Marin, F., Matt, G., Ursini, F., Middei, R., Marshall, H. L., Baldini, L., Barnouin, T., Rodriguez, N. Cavero, De Rosa, A., Di Gesu, L., Harper, D., Ingram, A., Karas, V., Krawczynski, H., Madejski, G., Panagiotou, C., Petrucci, P. O., Podgorny, J., Puccetti, S., Tombesi, F., Veledina, A., Zhang, W., Agudo, I., Antonelli, L. A., Bachetti, M., Baumgartner, W. H., Bellazzini, R., Bongiorno, S. D., Bonino, R., Brez, A., Bucciantini, N., Capitanio, F., Castellano, S., Cavazzuti, E., Ciprini, S., Costa, E., Del Monte, E., Di Lalla, N., Di Marco, A., Donnarumma, I., Doroshenko, V., Ehlert, S. R., Enoto, T., Evangelista, Y., Fabiani, S., Ferrazzoli, R., Garcia, J. A., Gunji, S., Hayashida, K., Heyl, J., Iwakiri, W., Jorstad, S. G., Kitaguchi, T., Kolodziejczak, J. J., La Monaca, F., Latronico, L., Liodakis, I., Maldera, S., Manfreda, A., Marscher, A. P., Mitsuishi, I., Mizuno, T., Ng, C. -Y., O'Dell, S. L., Omodei, N., Oppedisano, C., Papitto, A., Pavlov, G. G., Peirson, A. L., Perri, M., Pesce-Rollins, M., Pilia, M., Possenti, A., Poutanen, J., Ramsey, B. D., Rankin, J., Ratheesh, A., Romani, R. W., Sgrò, C., Slane, P., Soffitta, P., Spandre, G., Tamagawa, T., Tavecchio, F., Taverna, R., Tawara, Y., Tennant, A. F., Thomas, N. E., Trois, A., Tsygankov, S. S., Turolla, R., Vink, J., Weisskopf, M. C., Wu, K., Xie, F., and Zane, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) using polarized X-rays: the Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed with the Imaging X-ray Polarimetry Explorer (IXPE) starting on May 14, 2022 for a net observing time of 486 ks, simultaneously with XMM-Newton (58 ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at the 99% c.l.) is derived in the 2-8 keV energy range, where emission is dominated by the primary component ascribed to the hot corona. The broad-band spectrum, inferred from a simultaneous fit to the IXPE, NuSTAR, and XMM-Newton data, is well reproduced by a power law with photon index $\Gamma=1.85\pm0.01$ and a high-energy cutoff $E_{\rm C}=120\pm15$ keV. A comparison with Monte Carlo simulations shows that a lamp-post and a conical geometry of the corona are consistent with the observed upper limit, a slab geometry is allowed only if the inclination angle of the system is less than 50$^{\circ}$., Comment: 7 pages, 3 figures, 1 table. Submitted to MNRAS Letters
Published: 2022
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96. Limits on X-ray Polarization at the Core of Centaurus A as Observed with the Imaging X-ray Polarimetry Explorer

Author: Ehlert, Steven R., Ferrazzoli, Riccardo, Marinucci, Andrea, Marshall, Herman L., Middei, Riccardo, Pacciani, Luigi, Perri, Matteo, Petrucci, Pierre-Olivier, Puccetti, Simonetta, Barnouin, Thibault, Bianchi, Stefano, Liodakis, Ioannis, Madejski, Grzegorz, Marin, Fréderic, Marscher, Alan P., Matt, Giorgio, Poutanen, Juri, 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, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, 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, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Massaro, Francesco, 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., Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, 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, Zane, Silvia, Rodi, James, Jourdain, Elisabeth, and Roques, Jean-Pierre
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present measurements of the polarization of X-rays in the $2-8 \thinspace \mathrm{keV}$ band from the nucleus of the radio galaxy Centaurus A (Cen A), using a 100ks observation from the Imaging X-ray Polarimetry Explorer (IXPE). Nearly simultaneous observations of Cen A were also taken with the Swift, NuSTAR, and INTEGRAL observatories. No statistically significant degree of polarization is detected with IXPE. These observations have a minimum detectable polarization at $99 \%$ percent confidence (MDP$_{99}$) of $6.5 \%$ using a weighted, spectral model-independent calculation in the $2-8 \thinspace \mathrm{keV}$ band. The polarization angle $\psi$ is consequently unconstrained. Spectral fitting across three orders of magnitude in X-ray energy ($0.3-400 \thinspace \mathrm{keV}$) demonstrates that the SED of Cen A is well described by a simple power law with moderate intrinsic absorption ($N_H \sim 10^{23} \thinspace \mathrm{cm}^{-2}$) and a Fe K$\alpha$ emission line, although a second unabsorbed power law is required to account for the observed spectrum at energies below $2 \thinspace \mathrm{keV}$. This spectrum suggests that the reprocessing material responsible for this emission line is optically thin and distant from the central black hole. Our upper limits on the X-ray polarization are consistent with the predictions of Compton scattering, although the specific seed photon population responsible for production of the X-rays cannot be identified. The low polarization degree, variability in the core emission, and the relative lack of variability in the Fe K$\alpha$ emission line support a picture where electrons are accelerated in a region of highly disordered magnetic fields surrounding the innermost jet., Comment: Accepted for Publication in ApJ, 15 pages
Published: 2022
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97. Simultaneous space and phase resolved X-ray polarimetry of the Crab Pulsar and Nebula

Author: Bucciantini, Niccolò, Ferrazzoli, Riccardo, Bachetti, Matteo, Rankin, John, Di Lalla, Niccolò, Sgrò, Carmelo, Omodei, Nicola, Kitaguchi, Takao, Mizuno, Tsunefumi, Gunji, Shuichi, Watanabe, Eri, Baldini, Luca, Slane, Patrick, Weisskopf, Martin C., Romani, Roger W., Possenti, Andrea, Marshall, Herman L., Silvestri, Stefano, Pacciani, Luigi, Negro, Michela, Muleri, Fabio, Wilhelmi, Emma de Oña, Xie, Fei, Heyl, Jeremy, Pesce-Rollins, Melissa, Wong, Josephine, Pilia, Maura, Agudo, Ivan, Antonelli, Lucio A., Baumgartner, Wayne H., Bellazzini, Ronaldo, Bianchi, Stefano, Bongiorno, Stephen D., Bonino, Raffaella, Brez, Alessandro, Capitanio, Fiamma, Castellano, Simone, Cavazzuti, Elisabetta, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Dovčiak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Garcia, Javier A., Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Latronico, Luca, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marin, Frédéric, Marinucci, Andrea, Marscher, Alan P., Massaro, Francesco, Matt, Giorgio, Mitsuishi, Ikuyuki, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Petrucci, Pierre-Olivier, Poutanen, Juri, Puccetti, Simonetta, Ramsey, Brian D., Ratheesh, Ajay, Soffitta, Paolo, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Wu, Kinwah, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Crab pulsar and its nebula are among the most studied astrophysical systems, and constitute one of the most promising environments where high energy processes and particle acceleration can be investigated. They are the only objects for which previous X-ray polarisation has been reported. We present here the first Imaging X-ray Polarimetry Explorer (IXPE) observation of the Crab pulsar and nebula. The total pulsar pulsed emission in the [2-8] keV energy range is unpolarised. Significant polarisation up to 15% is detected only in the core of the main peak. The nebula has a total space integrated polarised degree of 20% and polarisation angle of 145deg. The polarised maps show a large variation in the local polarisation, and regions with polarised degree up to 45-50%. The polarisation pattern suggests a predominantly toroidal magnetic field., Comment: 29 pages, 7 figures, submitted to nature Astronomy - Includes Supplementary material
Published: 2022

98. Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1

Author: Krawczynski, Henric, Muleri, Fabio, Dovčiak, Michal, Veledina, Alexandra, Cavero, Nicole Rodriguez, Svoboda, Jiri, Ingram, Adam, Matt, Giorgio, Garcia, Javier A., Loktev, Vladislav, Negro, Michela, Poutanen, Juri, Kitaguchi, Takao, Podgorný, Jakub, Rankin, John, Zhang, Wenda, Berdyugin, Andrei, Berdyugina, Svetlana V., Bianchi, Stefano, Blinov, Dmitry, Capitanio, Fiamma, Di Lalla, Niccolò, Draghis, Paul, Fabiani, Sergio, Kagitani, Masato, Kravtsov, Vadim, Kiehlmann, Sebastian, Latronico, Luca, Lutovinov, Alexander A., Mandarakas, Nikos, Marin, Frédéric, Marinucci, Andrea, Miller, Jon, Mizuno, Tsunefumi, Molkov, Sergey V., Omodei, Nicola, Petrucci, Pierre-Olivier, Ratheesh, Ajay, Sakanoi, Takeshi, Semena, Andrei N., Skalidis, Raphael, Soffitta, Paolo, Tennant, Allyn F., Thalhammer, Phillipp, Tombesi, Francesco, Weisskopf, Martin C., Wilms, Joern, Zhang, Sixuan, 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, Ciprini, Stefano, Costa, Enrico, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Di Marco, Alessandro, Donnarumma, Immacolata, Doroshenko, Victor, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Ferrazzoli, Riccardo, Gunji, Shuichi, Hayashida, Kiyoshi, Heyl, Jeremy, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kolodziejczak, Jeffery J., La Monaca, Fabio, Liodakis, Ioannis, Maldera, Simone, Manfreda, Alberto, Marscher, Alan P., Marshall, Herman L., Mitsuishi, Ikuyuki, Ng, C. -Y., O'Dell, Stephen L., Oppedisano, Chiara, Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pesce-Rollins, Melissa, Pilia, Maura, Possenti, Andrea, Puccetti, Simonetta, Ramsey, Brian D., Romani, Roger W., Sgrò, Carmelo, Slane, Patrick, Spandre, Gloria, Tamagawa, Toru, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Thomas, Nicolas E., Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Vink, Jacco, Wu, Kinwah, Xie, Fei, and Zane, Silvia
Subjects: Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging x-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray emitting region. The polarization degree is (4.01+-0.20)% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. The observations reveal that hot x-ray emitting plasma is spatially extended in a plane perpendicular to the jet axis, not parallel to the jet., Comment: 51 pages, 15 figures, 5 tables
Published: 2022
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99. Calibration of the IXPE focal plane X-ray polarimeters to polarized radiation

Author: Di Marco, Alessandro, Fabiani, Sergio, La Monaca, Fabio, Muleri, Fabio, Rankin, John, Soffitta, Paolo, Xie, Fei, Amici, Fabrizio, attinà, Primo, Bachetti, Matteo, Baldini, Luca, Barbanera, Mattia, Baumgartner, Wayne, Bellazzini, Ronaldo, Borotto, Fabio, Brez, Alessandro, Brienza, Daniele, Caporale, Ciro, Cardelli, Claudia, Carpentiero, Rita, Castellano, Simone, Castronuovo, Marco, Cavalli, Luca, Cavazzuti, Elisabetta, Ceccanti, Marco, Centrone, Mauro, Citraro, Saverio, Costa, Enrico, D'Alba, Elisa, D'Amico, Fabio, Del Monte, Ettore, Di Cosimo, Sergio, Di Lalla, Niccolò, Di Persio, Giuseppe, Donnarumma, Immacolata, Evangelista, Yuri, Ferrazzoli, Riccardo, Latronico, Luca, Lefevre, Carlo, Loffredo, Pasqualino, Lorenzi, Paolo, Lucchesi, Leonardo, Magazzù, Carlo, Magazzù, Guido, Maldera, Simone, Manfreda, Alberto, Mangraviti, Elio, Marengo, Marco, Matt, Giorgio, Mereu, Paolo, Minuti, Massimo, Morbidini, Alfredo, Mosti, Federico, Nasimi, Hikmat, Negri, Barbara, Nuti, Alessio, O'Dell, Stephen L., Orsini, Leonardo, Perri, Matteo, Pesce-Rollins, Melissa, Piazzolla, Raffaele, Pieraccini, Stefano, Pilia, Maura, Pinchera, Michele, Profeti, Alessandro, Puccetti, Simonetta, Ramsey, Brian D., Ratheesh, Ajay, Rubini, Alda, Santoli, Francesco, Sarra, Paolo, Scalise, Emanuele, Sciortino, Andrea, Sgrò, Carmelo, Spandre, Gloria, Tardiola, Marcello, Tennant, Allyn F., Tobia, Antonino, Trois, Alessio, Vimercati, Marco, Weisskopf, Martin C., Zanetti, Davide, and Zanetti, Francesco
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: IXPE (Imaging X-ray Polarimetry Explorer) is a NASA Small Explorer mission -- in partnership with the Italian Space Agency (ASI) -- dedicated to X-ray polarimetry in the 2--8 keV energy band. The IXPE telescope comprises three grazing incidence mirror modules coupled to three detector units hosting each one a Gas Pixel Detector (GPD), a gas detector that allows measuring the polarization degree by using the photoelectric effect. A wide and accurate ground calibration was carried out on the IXPE Detector Units (DUs) at INAF-IAPS, in Italy, where a dedicated facility was set-up at this aim. In this paper, we present the results obtained from this calibration campaign to study the IXPE focal plane detector response to polarized radiation. In particular, we report on the modulation factor, which is the main parameter to estimate the sensitivity of a polarimeter., Comment: Accepted for publication on The Astronomical Journal
Published: 2022
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100. X-ray polarization detection of Cassiopeia A with IXPE

Author: Vink, Jacco, Prokhorov, Dmitry, Ferrazzoli, Riccardo, Slane, Patrick, Zhou, Ping, Asakura, Kazunori, Baldini, Luca, Bucciantini, Niccolo, Costa, Enrico, Di Marco, Alessandro, Heyl, Jeremy, Marin, Frederic, Mizuno, Tsunefumi, Ng, C. Y., Pesce-Rollins, Melissa, Ramsey, Brian D., Rankin, John, Ratheesh, Ajay, Sgro, Carmelo, Soffitta, Paolo, Swartz, Douglas A., Tamagawa, Toru, Weisskopf, Martin C., Yang, Yi-Jung, Bellazzini, Ronaldo, Bonino, Raffaella, Cavazzuti, Elisabetta, Costamante, Luigi, Di Lalla, Niccolo, Latronico, Luca, Maldera, Simone, Manfreda, Alberto, Massaro, Francesco, Mitsuishi, Ikuyuki, Omodei, Nicola, Oppedisano, Chiara, Zane, Silvia, Agudo, Ivan, Antonelli, Lucio A., Bachetti, Matteo, Baumgartner, Wayne H., Bianchi, Stefano, Bongiorno, Stephen D., Brez, Alessandro, Capitanio, Fiamma, Castellano, Simone, Ciprini, Stefano, De Rosa, Alessandra, Del Monte, Ettore, Di Gesu, Laura, Donnarumma, Immacolata, Doroshenko, Victor, Dovciak, Michal, Ehlert, Steven R., Enoto, Teruaki, Evangelista, Yuri, Fabiani, Sergio, Garcia, Javier A., Gunji, Shuichi, Hayashida, Kiyoshi, Iwakiri, Wataru, Jorstad, Svetlana G., Karas, Vladimir, Kitaguchi, Takao, Kolodziejczak, Jeffery J., Krawczynski, Henric, La Monaca, Fabio, Liodakis, Ioannis, Marinucci, Andrea, Marscher, Alan P., Marshall, Herman L., Matt, Giorgio, Muleri, Fabio, O'Dell, Stephen L., Papitto, Alessandro, Pavlov, George G., Peirson, Abel L., Perri, Matteo, Pilia, Maura, Possenti, Andrea, Poutanen, Juri, Puccetti, Simonetta, Romani, Roger W., Spandre, Gloria, Tavecchio, Fabrizio, Taverna, Roberto, Tawara, Yuzuru, Tennant, Allyn F., Thomas, Nicolas E., Tombesi, Francesco, Trois, Alessio, Tsygankov, Sergey, Turolla, Roberto, Wu, Kinwah, and Xie, Fei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on a $\sim 5\sigma$ detection of polarized 3-6 keV X-ray emission from the supernova remnant Cassiopeia A with the Imaging X-ray Polarimetry Explorer (IXPE). The overall polarization degree of $1.8 \pm 0.3$% is detected by summing over a large region, assuming circular symmetry for the polarization vectors. The measurements imply an average polarization degree for the synchrotron component of $\sim 2.5$%, and close to 5% for the X-ray synchrotron-domimated forward-shock region. These numbers are based on an assessment of the thermal and non-thermal radiation contributions, for which we used a detailed spatial-spectral model based on Chandra X-ray data. A pixel-by-pixel search for polarization provides a few tentative detections from discrete regions at the $\sim 3\sigma$ confidence level. Given the number of pixels, the significance is {insufficient} to claim a detection for individual pixels, but implies considerable turbulence on scales smaller than the angular resolution. Cas A's X-ray continuum emission is dominated by synchrotron radiation from regions within $\lesssim 10^{17}$ cm of the forward- and reverse shocks. We find that i) the measured polarization angle corresponds to a radially-oriented magnetic field, similar to what has been inferred from radio observations; ii) the X-ray polarization degree is lower than in the radio band ($\sim 5$%). Since shock compression should impose a tangential magnetic field structure, the IXPE results imply that magnetic-fields are reoriented within $\sim 10^{17}$cm of the shock. If the magnetic-field alignment is due to locally enhanced acceleration near quasi-parallel shocks, the preferred X-ray polarization angle suggests a size of $3\times 10^{16}$ cm for cells with radial magnetic fields., Comment: IXPE collaboration paper. Accepted by the Astrophysical Journal. This version reflects the version accepted by ApJ. With respect to version 1: new figures added to the Appendix and extension to the text, in particular the discussion section and Appendix
Published: 2022
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