The Astrophysical Journal (Jan 2024)

Tracking the X-Ray Polarization of the Black Hole Transient Swift J1727.8–1613 during a State Transition

  • Adam Ingram,
  • Niek Bollemeijer,
  • Alexandra Veledina,
  • Michal Dovčiak,
  • Juri Poutanen,
  • Elise Egron,
  • Thomas D. Russell,
  • Sergei A. Trushkin,
  • Michela Negro,
  • Ajay Ratheesh,
  • Fiamma Capitanio,
  • Riley Connors,
  • Joseph Neilsen,
  • Alexander Kraus,
  • Maria Noemi Iacolina,
  • Alberto Pellizzoni,
  • Maura Pilia,
  • Francesco Carotenuto,
  • Giorgio Matt,
  • Guglielmo Mastroserio,
  • Philip Kaaret,
  • Stefano Bianchi,
  • Javier A. García,
  • Matteo Bachetti,
  • Kinwah Wu,
  • Enrico Costa,
  • Melissa Ewing,
  • Vadim Kravtsov,
  • Henric Krawczynski,
  • Vladislav Loktev,
  • Andrea Marinucci,
  • Lorenzo Marra,
  • Romana Mikušincová,
  • Edward Nathan,
  • Maxime Parra,
  • Pierre-Olivier Petrucci,
  • Simona Righini,
  • Paolo Soffitta,
  • James F. Steiner,
  • Jiří Svoboda,
  • Francesco Tombesi,
  • Stefano Tugliani,
  • Francesco Ursini,
  • Yi-Jung Yang,
  • Silvia Zane,
  • Wenda Zhang,
  • Iván Agudo,
  • Lucio A. Antonelli,
  • Luca Baldini,
  • Wayne H. Baumgartner,
  • Ronaldo Bellazzini,
  • Stephen D. Bongiorno,
  • Raffaella Bonino,
  • Alessandro Brez,
  • Niccolò Bucciantini,
  • Simone Castellano,
  • Elisabetta Cavazzuti,
  • Chien-Ting Chen,
  • Stefano Ciprini,
  • Alessandra De Rosa,
  • Ettore Del Monte,
  • Laura Di Gesu,
  • Niccolò Di Lalla,
  • Alessandro Di Marco,
  • Immacolata Donnarumma,
  • Victor Doroshenko,
  • Steven R. Ehlert,
  • Teruaki Enoto,
  • Yuri Evangelista,
  • Sergio Fabiani,
  • Riccardo Ferrazzoli,
  • Shuichi Gunji,
  • Kiyoshi Hayashida,
  • Jeremy Heyl,
  • Wataru Iwakiri,
  • Svetlana G. Jorstad,
  • Vladimir Karas,
  • Fabian Kislat,
  • Takao Kitaguchi,
  • Jeffery J. Kolodziejczak,
  • Fabio La Monaca,
  • Luca Latronico,
  • Ioannis Liodakis,
  • Simone Maldera,
  • Alberto Manfreda,
  • Frédéric Marin,
  • Alan P. Marscher,
  • Herman L. Marshall,
  • Francesco Massaro,
  • Ikuyuki Mitsuishi,
  • Tsunefumi Mizuno,
  • Fabio Muleri,
  • Chi-Yung Ng,
  • Stephen L. O’Dell,
  • Nicola Omodei,
  • Chiara Oppedisano,
  • Alessandro Papitto,
  • George G. Pavlov,
  • Abel L. Peirson,
  • Matteo Perri,
  • Melissa Pesce-Rollins,
  • Andrea Possenti,
  • Simonetta Puccetti,
  • Brian D. Ramsey,
  • John Rankin,
  • Oliver J. Roberts,
  • Roger W. Romani,
  • Carmelo Sgrò,
  • Patrick Slane,
  • Gloria Spandre,
  • Douglas A. Swartz,
  • Toru Tamagawa,
  • Fabrizio Tavecchio,
  • Roberto Taverna,
  • Yuzuru Tawara,
  • Allyn F. Tennant,
  • Nicholas E. Thomas,
  • Alessio Trois,
  • Sergey S. Tsygankov,
  • Roberto Turolla,
  • Jacco Vink,
  • Martin C. Weisskopf,
  • Fei Xie,
  • IXPE Collaboration

DOI
https://doi.org/10.3847/1538-4357/ad3faf
Journal volume & issue
Vol. 968, no. 2
p. 76

Abstract

Read online

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.

Keywords