학술논문
Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5-1
Document Type
Working Paper
Author
Fabiani, Sergio; Capitanio, Fiamma; Iaria, Rosario; Poutanen, Juri; Gnarini, Andrea; Ursini, Francesco; Farinelli, Ruben; Bobrikova, Anna; Steiner, James F.; Svoboda, Jiri; Anitra, Alessio; Baglio, Maria C.; Carotenuto, Francesco; Del Santo, Melania; Ferrigno, Carlo; Lewis, Fraser; Russell, David M.; Russell, Thomas D.; Eijnden, Jakob van den; Cocchi, Massimo; Di Marco, Alessandro; La Monaca, Fabio; Liu, Kuan; Rankin, John; Weisskopf, Martin C.; Xie, Fei; Bianchi, Stefano; Burderi, Luciano; Di Salvo, Tiziana; Egron, Elise; Illiano, Giulia; Kaaret, Philip; Matt, Giorgio; Mikušincová, Romana; Muleri, Fabio; Papitto, Alessandro; Agudo, Iván; Antonelli, Lucio A.; Bachetti, Matteo; 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; Costa, Enrico; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccolò; Donnarumma, Immacolata; Doroshenko, Victor; Dovčiak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marin, Frédéric; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Mitsuishi, Ikuyuki; Mizuno, Tsunefumi; Negro, Michela; Ng, Chi-Yung; O'Dell, Stephen L.; Omodei, Nicola; Oppedisano, Chiara; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Pesce-Rollins, Melissa; Petrucci, Pierre-Olivier; Pilia, Maura; Possenti, Andrea; Puccetti, Simonetta; Ramsey, Brian D.; Ratheesh, Ajay; Roberts, Oliver J.; Romani, Roger W.; Sgrò, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Wu, Kinwah; Zane, Silvia
Source
Subject
Language
Abstract
We report on the coordinated observations of the neutron star low-mass X-ray binary (NS-LMXB) \gx 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 $3\sigma$ 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 which peaks in the mid- or far-IR. The X-ray polarization degree was found to be $3.7\% \pm 0.4 \%$ (at $90\%$ confidence level) during Obs.~1 when the source was in the horizontal branch of the Z-track and $1.8\% \pm 0.4 \%$ during Obs.~2 when the source was in the normal-flaring branch. These results confirm the variation of 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 for a variation of the polarization angle $\sim 20^\circ$ with energy is found in both observations, likely related to the different, non-orthogonal polarization angles of the disk and Comptonization components which peak at different energies.
Comment: Submitted to Astronomy and Astrophysics on 06 July 2023. Accepted on 21 November 2023
Comment: Submitted to Astronomy and Astrophysics on 06 July 2023. Accepted on 21 November 2023