TY - JOUR

T1 - Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5−1

AU - Fabiani, Sergio

AU - Capitanio, Fiamma

AU - Iaria, Rosario

AU - Poutanen, Juri

AU - Gnarini, Andrea

AU - Ursini, Francesco

AU - Farinelli, Ruben

AU - Bobrikova, Anna

AU - Steiner, James F.

AU - Svoboda, Jiri

AU - Anitra, Alessio

AU - Baglio, Maria C.

AU - Carotenuto, Francesco

AU - Del Santo, Melania

AU - Ferrigno, Carlo

AU - Lewis, Fraser

AU - Russell, David M.

AU - Russell, Thomas D.

AU - van den Eijnden, Jakob

AU - Cocchi, Massimo

AU - Di Marco, Alessandro

AU - La Monaca, Fabio

AU - Liu, Kuan

AU - Rankin, John

AU - Weisskopf, Martin C.

AU - Xie, Fei

AU - Bianchi, Stefano

AU - Burderi, Luciano

AU - Di Salvo, Tiziana

AU - Egron, Elise

AU - Illiano, Giulia

AU - Kaaret, Philip

AU - Matt, Giorgio

AU - Mikušincová, Romana

AU - Muleri, Fabio

AU - Papitto, Alessandro

AU - Agudo, Iván

AU - Antonelli, Lucio A.

AU - Bachetti, Matteo

AU - Baldini, Luca

AU - Baumgartner, Wayne H.

AU - Bellazzini, Ronaldo

AU - Bongiorno, Stephen D.

AU - Bonino, Raffaella

AU - Brez, Alessandro

AU - Bucciantini, Niccolò

AU - Castellano, Simone

AU - Cavazzuti, Elisabetta

AU - Chen, Chien-Ting

AU - Ciprini, Stefano

AU - Costa, Enrico

AU - De Rosa, Alessandra

AU - Del Monte, Ettore

AU - Di Gesu, Laura

AU - Di Lalla, Niccolò

AU - Donnarumma, Immacolata

AU - Doroshenko, Victor

AU - Dovčiak, Michal

AU - Ehlert, Steven R.

AU - Enoto, Teruaki

AU - Evangelista, Yuri

AU - Ferrazzoli, Riccardo

AU - Garcia, Javier A.

AU - Gunji, Shuichi

AU - Hayashida, Kiyoshi

AU - Heyl, Jeremy

AU - Iwakiri, Wataru

AU - Jorstad, Svetlana G.

AU - Karas, Vladimir

AU - Kislat, Fabian

AU - Kitaguchi, Takao

AU - Kolodziejczak, Jeffery J.

AU - Krawczynski, Henric

AU - Latronico, Luca

AU - Liodakis, Ioannis

AU - Maldera, Simone

AU - Manfreda, Alberto

AU - Marin, Frédéric

AU - Marinucci, Andrea

AU - Marscher, Alan P.

AU - Marshall, Herman L.

AU - Massaro, Francesco

AU - Mitsuishi, Ikuyuki

AU - Mizuno, Tsunefumi

AU - Negro, Michela

AU - Ng, Chi-Yung

AU - O'Dell, Stephen L.

AU - Omodei, Nicola

AU - Oppedisano, Chiara

AU - Pavlov, George G.

AU - Peirson, Abel L.

AU - Perri, Matteo

AU - Pesce-Rollins, Melissa

AU - Petrucci, Pierre-Olivier

AU - Pilia, Maura

AU - Possenti, Andrea

AU - Puccetti, Simonetta

AU - Ramsey, Brian D.

AU - Ratheesh, Ajay

AU - Roberts, Oliver J.

AU - Romani, Roger W.

AU - Sgrò, Carmelo

AU - Slane, Patrick

AU - Soffitta, Paolo

AU - Spandre, Gloria

AU - Swartz, Douglas A.

AU - Tamagawa, Toru

AU - Tavecchio, Fabrizio

AU - Taverna, Roberto

AU - Tawara, Yuzuru

AU - Tennant, Allyn F.

AU - Thomas, Nicholas E.

AU - Tombesi, Francesco

AU - Trois, Alessio

AU - Tsygankov, Sergey S.

AU - Turolla, Roberto

AU - Vink, Jacco

AU - Wu, Kinwah

AU - Zane, Silvia

PY - 2024/4/1

Y1 - 2024/4/1

N2 - 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.

AB - 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.

KW - accretion

KW - accretion disks

KW - stars: neutron

KW - X-rays: binaries

KW - X-rays: general

KW - X-rays: individuals: GX 5−1

KW - Astrophysics - High Energy Astrophysical Phenomena

U2 - 10.1051/0004-6361/202347374

DO - 10.1051/0004-6361/202347374

M3 - статья

VL - 684

SP - A137

JO - ASTRONOMY & ASTROPHYSICS

JF - ASTRONOMY & ASTROPHYSICS

SN - 0004-6361

ER -