Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1
H. Krawczynski, Fabio Muleri, Michal Dovčiak, Alexandra Veledina, Nicole Rodriguez Cavero, Jiří Svoboda, Adam Ingram, G. Matt, Javier A. García, Vladislav Loktev, Michela Negro, Juri Poutanen, Takao Kitaguchi, Jakub Podgorný, John Rankin, Wenda Zhang, A. Berdyugin, S. V. Berdyugina, S. Bianchi, D. Blinov, Fiamma Capitanio, Niccolò Di Lalla, Paul A. Draghis, Sergio Fabiani, Masato Kagitani, Vadim Kravtsov, S. Kiehlmann, L. Latronico, A. Lutovinov, Nikos Mandarakas, Frédéric Marin, Andrea Marinucci, J. M. Mïller, Tsunefumi Mizuno, S. Molkov, N. Omodei, Pierre-Olivier Petrucci, Ajay Ratheesh, Takeshi Sakanoi, A. Semena, Raphael Skalidis, P. Soffitta, Allyn F. Tennant, Phillipp Thalhammer, Francesco Tombesi, Martin C. Weisskopf, J. Wilms, 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, 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, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, W. Iwakiri, Svetlana G. Jorstad, V. Karas, Jeffery J. Kolodziejczak, Fabio La Monaca, Ioannis Liodakis, S. Maldera, Alberto Manfreda, Alan P. Marscher, Herman L. Marshall, Ikuyuki Mitsuishi, 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, Simonetta Puccetti, Brian D. Ramsey, Roger W. Romani, C. Sgró
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. These observations reveal that hot x-ray-emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis.