Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5-1

Sergio Fabiani, Fiamma Capitanio, Rosario Iaria, Andrea Gnarini, Francesco Ursini, Ruben Farinelli, Anna Bobrikova, James F. Steiner, Jiri Svoboda, Alessio Anitra, Maria C. Baglio, Francesco Carotenuto, Melania Del Santo, Carlo Ferrigno, Fraser Lewis, David M. Russell, Thomas D. Russell, Jakob Van Den Eijnden, Massimo Cocchi, Alessandro Di MarcoFabio La Monaca, John Rankin, Martin C. Weisskopf, Fei Xie, Stefano Bianchi, Luciano Burderi, Tiziana Di Salvo, Elise Egron, Giulia Illiano, Philip Kaaret, Giorgio Matt, Romana Mikušincová, Fabio Muleri, Alessandro Papitto, Ivań Agudo, Lucio A. Antonelli, Matteo Bachetti, 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, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Laura Di Gesu, Niccolò Di Lalla, Immacolata Donnarumma, Victor Doroshenko, Michal Dovčiak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Jeremy Heyl, Wataru Iwakiri, Svetlana G. Jorstad, Vladimir Karas, Fabian Kislat, Jeffery J. Kolodziejczak, Henric Krawczynski, Luca Latronico, Ioannis Liodakis, Simone Maldera, Alberto Manfreda, Frédéric Marin, Andrea Marinucci, Alan P. Marscher, Herman L. Marshall, Francesco Massaro, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Michela Negro, Chi Yung Ng, Stephen L. O'Dell, Nicola Omodei, Chiara Oppedisano, George G. Pavlov, Abel L. Peirson, Matteo Perri, Melissa Pesce-Rollins, Pierre Olivier Petrucci, Maura Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, Ajay Ratheesh, Oliver J. Roberts, Roger W. Romani, Carmelo Sgrò, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Fabrizio Tavecchio, Roberto Taverna, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi, Alessio Trois, Sergey S. Tsygankov, Roberto Turolla, Jacco Vink, Kinwah Wu, Silvia Zane, Juri Poutanen, Kuan Liu, Yuzuru Tawara, Takao Kitaguchi

Research output: Contribution to journalArticlepeer-review

Abstract

We report on the coordinated observations of the neutron star low-mass X-ray binary (NS-LMXB) GX 5-1 in X-rays (IXPE, NICER, NuSTAR, and INTEGRAL), optical (REM and LCO), near-infrared (REM), mid-infrared (VLT VISIR), and radio (ATCA). This Z-source was observed by IXPE twice in March-April 2023 (Obs. 1 and 2). In the radio band the source was detected, but only upper limits to the linear polarization were obtained at a 3σ level of 6.1% at 5.5 GHz and 5.9% at 9 GHz in Obs. 1 and 12.5% at 5.5 GHz and 20% at 9 GHz in Obs. 2. The mid-IR, near-IR, and optical observations suggest the presence of a compact jet that peaks in the mid-or far-IR. The X-ray polarization degree was found to be 3:7% ± 0:4% (at 90% confidence level) during Obs. 1 when the source was in the horizontal branch of the Z-Track and 1:8% ± 0:4% during Obs. 2 when the source was in the normal-flaring branch. These results confirm the variation in polarization degree as a function of the position of the source in the color-color diagram, as for previously observed Z-Track sources (Cyg X-2 and XTE 1701-462). Evidence of a variation in the polarization angle of ∼20° with energy is found in both observations, likely related to the different, nonorthogonal polarization angles of the disk and Comptonization components, which peak at different energies.

Original languageEnglish (US)
Article numberA137
JournalAstronomy and Astrophysics
Volume684
DOIs
StatePublished - Apr 1 2024

Keywords

  • Accretion
  • Accretion disks
  • X-rays: binaries
  • X-rays: general
  • X-rays: individuals: GX 5-1
  • stars: neutron

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5-1'. Together they form a unique fingerprint.

Cite this