Standard
An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing. / Steiner, James F.; Nathan, Edward; Hu, Kun; Krawczynski, Henric; Dovčiak, Michal; Veledina, Alexandra; Muleri, Fabio; Svoboda, Jiri; Alabarta, Kevin; Parra, Maxime; Bhargava, Yash; Matt, Giorgio; Poutanen, Juri; Petrucci, Pierre-Olivier; Tennant, Allyn F.; Baglio, M. Cristina; Baldini, Luca; Barnier, Samuel; Bhattacharyya, Sudip; Bianchi, Stefano; Brigitte, Maimouna; Cabezas, Mauricio; Cangemi, Floriane; Capitanio, Fiamma; Casey, Jacob; Rodriguez Cavero, Nicole; Castellano, Simone; Cavazzuti, Elisabetta; Chun, Sohee; Churazov, Eugene; Costa, Enrico; Di Lalla, Niccolò; Di Marco, Alessandro; Egron, Elise; Ewing, Melissa; Fabiani, Sergio; García, Javier A.; Green, David A.; Grinberg, Victoria; Hadrava, Petr; Ingram, Adam; Kaaret, Philip; Kislat, Fabian; Kitaguchi, Takao; Kravtsov, Vadim; Kubátová, Brankica; La Monaca, Fabio; Latronico, Luca; Loktev, Vladislav; Malacaria, Christian; Marin, Frédéric; Marinucci, Andrea; Maryeva, Olga; Mastroserio, Guglielmo; Mizuno, Tsunefumi; Negro, Michela; Omodei, Nicola; Podgorný, Jakub; Rankin, John; Ratheesh, Ajay; Rhodes, Lauren; Russell, David M.; Šlechta, Miroslav; Soffitta, Paolo; Spooner, Sean; Suleimanov, Valery; Tombesi, Francesco; Trushkin, Sergei A.; Weisskopf, Martin C.; Zane, Silvia; Zdziarski, Andrzej A.; Zhang, Sixuan; Zhang, Wenda; Zhou, Menglei; Agudo, Iván; Antonelli, Lucio A.; Bachetti, Matteo; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Bucciantini, Niccolò; Chen, Chien-Ting; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; 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.; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Mitsuishi, Ikuyuki; Ng, Chi-Yung; 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.; Roberts, Oliver J.; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Thomas, Nicholas E.; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Xie, Fei.
In:
The Astrophysical Journal, Vol. 969, No. 2, L30, 01.07.2024.
Research output: Contribution to journal › Article › peer-review
Harvard
Steiner, JF, Nathan, E, Hu, K, Krawczynski, H, Dovčiak, M, Veledina, A, Muleri, F, Svoboda, J, Alabarta, K, Parra, M, Bhargava, Y, Matt, G, Poutanen, J, Petrucci, P-O, Tennant, AF, Baglio, MC, Baldini, L, Barnier, S, Bhattacharyya, S, Bianchi, S, Brigitte, M, Cabezas, M, Cangemi, F, Capitanio, F, Casey, J, Rodriguez Cavero, N, Castellano, S, Cavazzuti, E, Chun, S, Churazov, E, Costa, E, Di Lalla, N, Di Marco, A, Egron, E, Ewing, M, Fabiani, S, García, JA, Green, DA, Grinberg, V, Hadrava, P, Ingram, A, Kaaret, P, Kislat, F, Kitaguchi, T
, Kravtsov, V, Kubátová, B, La Monaca, F, Latronico, L
, Loktev, V, Malacaria, C, Marin, F, Marinucci, A, Maryeva, O, Mastroserio, G, Mizuno, T, Negro, M, Omodei, N, Podgorný, J, Rankin, J, Ratheesh, A, Rhodes, L, Russell, DM, Šlechta, M, Soffitta, P, Spooner, S, Suleimanov, V, Tombesi, F, Trushkin, SA, Weisskopf, MC, Zane, S, Zdziarski, AA, Zhang, S, Zhang, W, Zhou, M, Agudo, I, Antonelli, LA, Bachetti, M, Baumgartner, WH, Bellazzini, R, Bongiorno, SD, Bonino, R, Brez, A, Bucciantini, N, Chen, C-T, Ciprini, S, De Rosa, A, Del Monte, E, Di Gesu, L, Donnarumma, I, Doroshenko, V, Ehlert, SR, Enoto, T, Evangelista, Y, Ferrazzoli, R, Gunji, S, Hayashida, K, Heyl, J, Iwakiri, W
, Jorstad, SG, Karas, V, Kolodziejczak, JJ, Liodakis, I, Maldera, S, Manfreda, A, Marscher, AP, Marshall, HL, Massaro, F, Mitsuishi, I, Ng, C-Y, O'Dell, SL, Oppedisano, C, Papitto, A, Pavlov, GG, Peirson, AL, Perri, M, Pesce-Rollins, M, Pilia, M, Possenti, A, Puccetti, S, Ramsey, BD, Roberts, OJ, Romani, RW, Sgrò, C, Slane, P, Spandre, G, Swartz, DA, Tamagawa, T, Tavecchio, F, Taverna, R, Tawara, Y, Thomas, NE, Trois, A, Tsygankov, SS, Turolla, R, Vink, J, Wu, K & Xie, F 2024, '
An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing',
The Astrophysical Journal, vol. 969, no. 2, L30.
https://doi.org/10.3847/2041-8213/ad58e4APA
Steiner, J. F., Nathan, E., Hu, K., Krawczynski, H., Dovčiak, M., Veledina, A., Muleri, F., Svoboda, J., Alabarta, K., Parra, M., Bhargava, Y., Matt, G., Poutanen, J., Petrucci, P-O., Tennant, A. F., Baglio, M. C., Baldini, L., Barnier, S., Bhattacharyya, S., ... Xie, F. (2024).
An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing.
The Astrophysical Journal,
969(2), [L30].
https://doi.org/10.3847/2041-8213/ad58e4Vancouver
Author
Steiner, James F. ; Nathan, Edward ; Hu, Kun ; Krawczynski, Henric ; Dovčiak, Michal ; Veledina, Alexandra ; Muleri, Fabio ; Svoboda, Jiri ; Alabarta, Kevin ; Parra, Maxime ; Bhargava, Yash ; Matt, Giorgio ; Poutanen, Juri ; Petrucci, Pierre-Olivier ; Tennant, Allyn F. ; Baglio, M. Cristina ; Baldini, Luca ; Barnier, Samuel ; Bhattacharyya, Sudip ; Bianchi, Stefano ; Brigitte, Maimouna ; Cabezas, Mauricio ; Cangemi, Floriane ; Capitanio, Fiamma ; Casey, Jacob ; Rodriguez Cavero, Nicole ; Castellano, Simone ; Cavazzuti, Elisabetta ; Chun, Sohee ; Churazov, Eugene ; Costa, Enrico ; Di Lalla, Niccolò ; Di Marco, Alessandro ; Egron, Elise ; Ewing, Melissa ; Fabiani, Sergio ; García, Javier A. ; Green, David A. ; Grinberg, Victoria ; Hadrava, Petr ; Ingram, Adam ; Kaaret, Philip ; Kislat, Fabian ; Kitaguchi, Takao
; Kravtsov, Vadim ; Kubátová, Brankica ; La Monaca, Fabio ; Latronico, Luca
; Loktev, Vladislav ; Malacaria, Christian ; Marin, Frédéric ; Marinucci, Andrea ; Maryeva, Olga ; Mastroserio, Guglielmo ; Mizuno, Tsunefumi ; Negro, Michela ; Omodei, Nicola ; Podgorný, Jakub ; Rankin, John ; Ratheesh, Ajay ; Rhodes, Lauren ; Russell, David M. ; Šlechta, Miroslav ; Soffitta, Paolo ; Spooner, Sean ; Suleimanov, Valery ; Tombesi, Francesco ; Trushkin, Sergei A. ; Weisskopf, Martin C. ; Zane, Silvia ; Zdziarski, Andrzej A. ; Zhang, Sixuan ; Zhang, Wenda ; Zhou, Menglei ; Agudo, Iván ; Antonelli, Lucio A. ; Bachetti, Matteo ; Baumgartner, Wayne H. ; Bellazzini, Ronaldo ; Bongiorno, Stephen D. ; Bonino, Raffaella ; Brez, Alessandro ; Bucciantini, Niccolò ; Chen, Chien-Ting ; Ciprini, Stefano ; De Rosa, Alessandra ; Del Monte, Ettore ; Di Gesu, Laura ; 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. ; Liodakis, Ioannis ; Maldera, Simone ; Manfreda, Alberto ; Marscher, Alan P. ; Marshall, Herman L. ; Massaro, Francesco ; Mitsuishi, Ikuyuki ; Ng, Chi-Yung ; 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. ; Roberts, Oliver J. ; Romani, Roger W. ; Sgrò, Carmelo ; Slane, Patrick ; Spandre, Gloria ; Swartz, Douglas A. ; Tamagawa, Toru ; Tavecchio, Fabrizio ; Taverna, Roberto ; Tawara, Yuzuru ; Thomas, Nicholas E. ; Trois, Alessio ; Tsygankov, Sergey S. ; Turolla, Roberto ; Vink, Jacco ; Wu, Kinwah ; Xie, Fei. /
An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing. In:
The Astrophysical Journal. 2024 ; Vol. 969, No. 2.
BibTeX
@article{4834ce5cc5af47198d7d240746a1bfb2,
title = "An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing",
abstract = "We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May–June. Companion multiwavelength data during the campaign are likewise shown. The 2–8 keV X-rays exhibit a net polarization degree PD = 1.99% ± 0.13% (68% confidence). The polarization signal is found to increase with energy across the Imaging X-ray Polarimetry Explorer's (IXPE) 2–8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA = ‑25.°7 ± 1.°8 east of north (68% confidence). This is consistent with being aligned to Cyg X-1's au-scale compact radio jet and its parsec-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trend line in the polarization degree between the soft and hard states. Our favored polarimetric model indicates that Cyg X-1's spin is likely high (a * ≳ 0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.",
keywords = "Accretion, Polarimetry, X-ray astronomy, Stellar mass black holes, 14, 1278, 1810, 1611, Astrophysics - High Energy Astrophysical Phenomena",
author = "Steiner, {James F.} and Edward Nathan and Kun Hu and Henric Krawczynski and Michal Dov{\v c}iak and Alexandra Veledina and Fabio Muleri and Jiri Svoboda and Kevin Alabarta and Maxime Parra and Yash Bhargava and Giorgio Matt and Juri Poutanen and Pierre-Olivier Petrucci and Tennant, {Allyn F.} and Baglio, {M. Cristina} and Luca Baldini and Samuel Barnier and Sudip Bhattacharyya and Stefano Bianchi and Maimouna Brigitte and Mauricio Cabezas and Floriane Cangemi and Fiamma Capitanio and Jacob Casey and {Rodriguez Cavero}, Nicole and Simone Castellano and Elisabetta Cavazzuti and Sohee Chun and Eugene Churazov and Enrico Costa and {Di Lalla}, Niccol{\`o} and {Di Marco}, Alessandro and Elise Egron and Melissa Ewing and Sergio Fabiani and Garc{\'i}a, {Javier A.} and Green, {David A.} and Victoria Grinberg and Petr Hadrava and Adam Ingram and Philip Kaaret and Fabian Kislat and Takao Kitaguchi and Vadim Kravtsov and Brankica Kub{\'a}tov{\'a} and {La Monaca}, Fabio and Luca Latronico and Vladislav Loktev and Christian Malacaria and Fr{\'e}d{\'e}ric Marin and Andrea Marinucci and Olga Maryeva and Guglielmo Mastroserio and Tsunefumi Mizuno and Michela Negro and Nicola Omodei and Jakub Podgorn{\'y} and John Rankin and Ajay Ratheesh and Lauren Rhodes and Russell, {David M.} and Miroslav {\v S}lechta and Paolo Soffitta and Sean Spooner and Valery Suleimanov and Francesco Tombesi and Trushkin, {Sergei A.} and Weisskopf, {Martin C.} and Silvia Zane and Zdziarski, {Andrzej A.} and Sixuan Zhang and Wenda Zhang and Menglei Zhou and Iv{\'a}n Agudo and Antonelli, {Lucio A.} and Matteo Bachetti and Baumgartner, {Wayne H.} and Ronaldo Bellazzini and Bongiorno, {Stephen D.} and Raffaella Bonino and Alessandro Brez and Niccol{\`o} Bucciantini and Chien-Ting Chen and Stefano Ciprini and {De Rosa}, Alessandra and {Del Monte}, Ettore and {Di Gesu}, Laura and Immacolata Donnarumma and Victor Doroshenko and Ehlert, {Steven R.} and Teruaki Enoto and Yuri Evangelista and Riccardo Ferrazzoli and Shuichi Gunji and Kiyoshi Hayashida and Jeremy Heyl and Wataru Iwakiri and Jorstad, {Svetlana G.} and Vladimir Karas and Kolodziejczak, {Jeffery J.} and Ioannis Liodakis and Simone Maldera and Alberto Manfreda and Marscher, {Alan P.} and Marshall, {Herman L.} and Francesco Massaro and Ikuyuki Mitsuishi and Chi-Yung Ng and O'Dell, {Stephen L.} and Chiara Oppedisano and Alessandro Papitto and Pavlov, {George G.} and Peirson, {Abel L.} and Matteo Perri and Melissa Pesce-Rollins and Maura Pilia and Andrea Possenti and Simonetta Puccetti and Ramsey, {Brian D.} and Roberts, {Oliver J.} and Romani, {Roger W.} and Carmelo Sgr{\`o} and Patrick Slane and Gloria Spandre and Swartz, {Douglas A.} and Toru Tamagawa and Fabrizio Tavecchio and Roberto Taverna and Yuzuru Tawara and Thomas, {Nicholas E.} and Alessio Trois and Tsygankov, {Sergey S.} and Roberto Turolla and Jacco Vink and Kinwah Wu and Fei Xie",
year = "2024",
month = jul,
day = "1",
doi = "10.3847/2041-8213/ad58e4",
language = "English",
volume = "969",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",
}
RIS
TY - JOUR
T1 - An IXPE-led X-Ray Spectropolarimetric Campaign on the Soft State of Cygnus X-1: X-Ray Polarimetric Evidence for Strong Gravitational Lensing
AU - Steiner, James F.
AU - Nathan, Edward
AU - Hu, Kun
AU - Krawczynski, Henric
AU - Dovčiak, Michal
AU - Veledina, Alexandra
AU - Muleri, Fabio
AU - Svoboda, Jiri
AU - Alabarta, Kevin
AU - Parra, Maxime
AU - Bhargava, Yash
AU - Matt, Giorgio
AU - Poutanen, Juri
AU - Petrucci, Pierre-Olivier
AU - Tennant, Allyn F.
AU - Baglio, M. Cristina
AU - Baldini, Luca
AU - Barnier, Samuel
AU - Bhattacharyya, Sudip
AU - Bianchi, Stefano
AU - Brigitte, Maimouna
AU - Cabezas, Mauricio
AU - Cangemi, Floriane
AU - Capitanio, Fiamma
AU - Casey, Jacob
AU - Rodriguez Cavero, Nicole
AU - Castellano, Simone
AU - Cavazzuti, Elisabetta
AU - Chun, Sohee
AU - Churazov, Eugene
AU - Costa, Enrico
AU - Di Lalla, Niccolò
AU - Di Marco, Alessandro
AU - Egron, Elise
AU - Ewing, Melissa
AU - Fabiani, Sergio
AU - García, Javier A.
AU - Green, David A.
AU - Grinberg, Victoria
AU - Hadrava, Petr
AU - Ingram, Adam
AU - Kaaret, Philip
AU - Kislat, Fabian
AU - Kitaguchi, Takao
AU - Kravtsov, Vadim
AU - Kubátová, Brankica
AU - La Monaca, Fabio
AU - Latronico, Luca
AU - Loktev, Vladislav
AU - Malacaria, Christian
AU - Marin, Frédéric
AU - Marinucci, Andrea
AU - Maryeva, Olga
AU - Mastroserio, Guglielmo
AU - Mizuno, Tsunefumi
AU - Negro, Michela
AU - Omodei, Nicola
AU - Podgorný, Jakub
AU - Rankin, John
AU - Ratheesh, Ajay
AU - Rhodes, Lauren
AU - Russell, David M.
AU - Šlechta, Miroslav
AU - Soffitta, Paolo
AU - Spooner, Sean
AU - Suleimanov, Valery
AU - Tombesi, Francesco
AU - Trushkin, Sergei A.
AU - Weisskopf, Martin C.
AU - Zane, Silvia
AU - Zdziarski, Andrzej A.
AU - Zhang, Sixuan
AU - Zhang, Wenda
AU - Zhou, Menglei
AU - Agudo, Iván
AU - Antonelli, Lucio A.
AU - Bachetti, Matteo
AU - Baumgartner, Wayne H.
AU - Bellazzini, Ronaldo
AU - Bongiorno, Stephen D.
AU - Bonino, Raffaella
AU - Brez, Alessandro
AU - Bucciantini, Niccolò
AU - Chen, Chien-Ting
AU - Ciprini, Stefano
AU - De Rosa, Alessandra
AU - Del Monte, Ettore
AU - Di Gesu, Laura
AU - Donnarumma, Immacolata
AU - Doroshenko, Victor
AU - Ehlert, Steven R.
AU - Enoto, Teruaki
AU - Evangelista, Yuri
AU - Ferrazzoli, Riccardo
AU - Gunji, Shuichi
AU - Hayashida, Kiyoshi
AU - Heyl, Jeremy
AU - Iwakiri, Wataru
AU - Jorstad, Svetlana G.
AU - Karas, Vladimir
AU - Kolodziejczak, Jeffery J.
AU - Liodakis, Ioannis
AU - Maldera, Simone
AU - Manfreda, Alberto
AU - Marscher, Alan P.
AU - Marshall, Herman L.
AU - Massaro, Francesco
AU - Mitsuishi, Ikuyuki
AU - Ng, Chi-Yung
AU - O'Dell, Stephen L.
AU - Oppedisano, Chiara
AU - Papitto, Alessandro
AU - Pavlov, George G.
AU - Peirson, Abel L.
AU - Perri, Matteo
AU - Pesce-Rollins, Melissa
AU - Pilia, Maura
AU - Possenti, Andrea
AU - Puccetti, Simonetta
AU - Ramsey, Brian D.
AU - Roberts, Oliver J.
AU - Romani, Roger W.
AU - Sgrò, Carmelo
AU - Slane, Patrick
AU - Spandre, Gloria
AU - Swartz, Douglas A.
AU - Tamagawa, Toru
AU - Tavecchio, Fabrizio
AU - Taverna, Roberto
AU - Tawara, Yuzuru
AU - Thomas, Nicholas E.
AU - Trois, Alessio
AU - Tsygankov, Sergey S.
AU - Turolla, Roberto
AU - Vink, Jacco
AU - Wu, Kinwah
AU - Xie, Fei
PY - 2024/7/1
Y1 - 2024/7/1
N2 - We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May–June. Companion multiwavelength data during the campaign are likewise shown. The 2–8 keV X-rays exhibit a net polarization degree PD = 1.99% ± 0.13% (68% confidence). The polarization signal is found to increase with energy across the Imaging X-ray Polarimetry Explorer's (IXPE) 2–8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA = ‑25.°7 ± 1.°8 east of north (68% confidence). This is consistent with being aligned to Cyg X-1's au-scale compact radio jet and its parsec-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trend line in the polarization degree between the soft and hard states. Our favored polarimetric model indicates that Cyg X-1's spin is likely high (a * ≳ 0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.
AB - We present the first X-ray spectropolarimetric results for Cygnus X-1 in its soft state from a campaign of five IXPE observations conducted during 2023 May–June. Companion multiwavelength data during the campaign are likewise shown. The 2–8 keV X-rays exhibit a net polarization degree PD = 1.99% ± 0.13% (68% confidence). The polarization signal is found to increase with energy across the Imaging X-ray Polarimetry Explorer's (IXPE) 2–8 keV bandpass. The polarized X-rays exhibit an energy-independent polarization angle of PA = ‑25.°7 ± 1.°8 east of north (68% confidence). This is consistent with being aligned to Cyg X-1's au-scale compact radio jet and its parsec-scale radio lobes. In comparison to earlier hard-state observations, the soft state exhibits a factor of 2 lower polarization degree but a similar trend with energy and a similar (also energy-independent) position angle. When scaling by the natural unit of the disk temperature, we find the appearance of a consistent trend line in the polarization degree between the soft and hard states. Our favored polarimetric model indicates that Cyg X-1's spin is likely high (a * ≳ 0.96). The substantial X-ray polarization in Cyg X-1's soft state is most readily explained as resulting from a large portion of X-rays emitted from the disk returning and reflecting off the disk surface, generating a high polarization degree and a polarization direction parallel to the black hole spin axis and radio jet. In IXPE's bandpass, the polarization signal is dominated by the returning reflection emission. This constitutes polarimetric evidence for strong gravitational lensing of X-rays close to the black hole.
KW - Accretion
KW - Polarimetry
KW - X-ray astronomy
KW - Stellar mass black holes
KW - 14
KW - 1278
KW - 1810
KW - 1611
KW - Astrophysics - High Energy Astrophysical Phenomena
UR - https://www.mendeley.com/catalogue/b3a9b8c2-e50b-31e1-8d5c-e2ae13023068/
U2 - 10.3847/2041-8213/ad58e4
DO - 10.3847/2041-8213/ad58e4
M3 - Article
VL - 969
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - L30
ER -
