A1 Refereed original research article in a scientific journal
Tracking the X-Ray Polarization of the Black Hole Transient Swift J1727.8-1613 during a State Transition
Authors: Ingram, Adam; Bollemeijer, Niek; Veledina, Alexandra; Dovčiak, Michal; Poutanen, Juri; Egron, Elise; Russell, Thomas D.; Trushkin, Sergei A.; Negro, Michela; Ratheesh, Ajay; Capitanio, Fiamma; Connors, Riley; Neilsen, Joseph; Kraus, Alexander; Iacolina, Maria Noemi; Pellizzoni, Alberto; Pilia, Maura; Carotenuto, Francesco; Matt, Giorgio; Mastroserio, Guglielmo; Kaaret, Philip; Bianchi, Stefano; García, Javier A.; Bachetti, Matteo; Wu, Kinwah; Costa, Enrico; Ewing, Melissa; Kravtsov, Vadim; Krawczynski, Henric; Loktev, Vladislav; Marinucci, Andrea; Marra, Lorenzo; Mikušincová, Romana; Nathan, Edward; Parra, Maxime; Petrucci, Pierre-Olivier; Righini, Simona; Soffitta, Paolo; Steiner, James F.; Svoboda, Jiří; Tombesi, Francesco; Tugliani, Stefano; Ursini, Francesco; Yang, Yi-Jung; Zane, Silvia; Zhang, Wenda; Agudo, Iván; Antonelli, Lucio A.; 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; 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; 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, Frédéric; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Muleri, Fabio; Ng, Chi-Yung; O’Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Possenti, Andrea; Puccetti, Simonetta; Ramsey, Brian D.; Rankin, John; Roberts, Oliver J.; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Weisskopf, Martin C.; Xie, Fei; IXPE Collaboration
Publisher: Institute of Physics
Publication year: 2024
Journal: Astrophysical Journal
Journal name in source: Astrophysical Journal
Article number: 76
Volume: 968
Issue: 2
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ad3faf
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ad3faf
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/457083750
Preprint address: https://arxiv.org/abs/2311.05497
We report on an observational campaign on the bright black hole (BH) X-ray binary Swift J1727.8-1613 centered around five observations by the Imaging X-ray Polarimetry Explorer. These observations track for the first time the evolution of the X-ray polarization of a BH X-ray binary across a hard to soft state transition. The 2-8 keV polarization degree decreased from ∼4% to ∼3% across the five observations, but the polarization angle remained oriented in the north-south direction throughout. Based on observations with the Australia Telescope Compact Array, we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher-spatial-resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long (≳10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8-1613 is a member of a hitherto undersampled subpopulation.
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Funding information in the publication:
A.I. acknowledges support from the Royal Society. A.V. thanks the Academy of Finland grant No. 355672 for support. M.D., J.S., and V.K. thank GACR project 21-06825X for the support and institutional support from RVO:67985815. T.D.R. is an INAF Research Fellow. H.K. acknowledges support by NASA grant Nos. 80NSSC22K1291, 80NSSC23K1041, and 80NSSC20K0329. The French contribution is supported by the French Space Agency (Centre National d'Etude Spatiale, CNES) and by the High Energy National Programme (PNHE) of the Centre National de la Recherche Scientifique (CNRS). V.K. acknowledges support from the Finnish Cultural Foundation.
