X-Ray Polarization of the Black Hole X-Ray Binary 4U 1630–47 Challenges the Standard Thin Accretion Disk Scenario
Ajay Ratheesh, Michal Dovčiak, H. Krawczynski, Jakub Podgorný, Lorenzo Marra, Alexandra Veledina, В. Ф. Сулейманов, Nicole Rodriguez Cavero, James F. Steiner, Jiří Svoboda, Andrea Marinucci, S. Bianchi, Michela Negro, G. Matt, Francesco Tombesi, Juri Poutanen, Adam Ingram, Roberto Taverna, Andrew West, V. Karas, F. Ursini, P. Soffitta, Fiamma Capitanio, Domenico Viscolo, Alberto Manfreda, Fabio Muleri, Maxime Parra, Banafsheh Beheshtipour, Sohee Chun, Nicolò Cibrario, Niccolò Di Lalla, Sergio Fabiani, Kun Hu, P. Kaaret, Vladislav Loktev, Romana Mikušincová, Tsunefumi Mizuno, N. Omodei, Pierre-Olivier Petrucci, Simonetta Puccetti, John Rankin, Silvia Zane, Sixuan Zhang, I. Agudo, L. A. Antonelli, Matteo Bachetti, L. Baldini, W. H. Baumgartner, R. Bellazzini, Stephen D. Bongiorno, R. Bonino, A. Brez, N. Bucciantini, Simone Castellano, E. Cavazzuti, Chien‐Ting Chen, S. Ciprini, E. Costa, Alessandra De Rosa, E. Del Monte, Laura Di Gesu, Alessandro Di Marco, I. Donnarumma, Victor Doroshenko, Steven R. Ehlert, Teruaki Enoto, Y. Evangelista, Riccardo Ferrazzoli, Javier A. García, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, W. Iwakiri, S. G. Jorstad, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak, Fabio La Monaca, L. Latronico, Ioannis Liodakis, S. Maldera, Frédéric Marin, Alan P. Marscher, Herman L. Marshall, F. Massaro, Ikuyuki Mitsuishi, Stephen C. Y. Ng, Stephen L. O’Dell, C. Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, M. Perri, M. Pesce-Rollins, M. Pilia, Andrea Possenti, Brian D. Ramsey, O. J. Roberts, Roger W. Romani, C. Sgró
Abstract
Abstract A 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 ≈50 σ confidence level) of an unexpectedly high polarization, rising from ∼6% at 2 keV to ∼10% at 8 keV, cannot be easily reconciled with standard models of thin accretion disks. 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 disk covered by a partially ionized atmosphere flowing away at mildly relativistic velocities.