| Title: |
Discovery of a variable energy-dependent X-ray polarization in the accreting neutron star GX 5-1 |
| Authors: |
Fabiani, S; Capitanio, F; Iaria, R; Gnarini, A; Ursini, F; Farinelli, R; Bobrikova, A; Steiner, JF; Svoboda, J; Anitra, A; Baglio, MC; Carotenuto, F; Santo, MD; Ferrigno, C; Lewis, F; Russell, DM; Russell, TD; Van Den Eijnden, J; Cocchi, M; Marco, AD; Monaca, FL; Rankin, J; Weisskopf, MC; Xie, F; Bianchi, S; Burderi, L; Di Salvo, T; Egron, E; Illiano, G; Kaaret, P; Matt, G; Mikušincová, R; Muleri, F; Papitto, A; Agudo, I; Antonelli, LA; Bachetti, M; Baldini, L; Baumgartner, WH; Bellazzini, R; Bongiorno, SD; Bonino, R; Brez, A; Bucciantini, N; Castellano, S; Cavazzuti, E; Chen, CT; Ciprini, S; Costa, E; De Rosa, A; Del Monte, E; Di Gesu, L; Di Lalla, N; Donnarumma, I; Doroshenko, V; Dovčiak, M; Ehlert, SR; Enoto, T; Evangelista, Y; Ferrazzoli, R; Garcia, JA; Gunji, S; Hayashida, K; Heyl, J; Iwakiri, W; Jorstad, SG; Karas, V; Kislat, F; Kolodziejczak, JJ; Krawczynski, H; Latronico, L; Liodakis, I; Maldera, S; Manfreda, A; Marin, F; Marinucci, A; Marscher, AP; Marshall, HL; Massaro, F; Mitsuishi, I; Mizuno, T; Negro, M; Ng, CY; O'Dell, SL; Omodei, N; Oppedisano, C; Pavlov, GG; Peirson, AL; Perri, M; Pesce-Rollins, M; Petrucci, PO; Pilia, M; Possenti, A; Puccetti, S; Ramsey, BD; Ratheesh, A; Roberts, OJ; Romani, RW; Sgrò, C; Slane, P |
| Publisher Information: |
EDP Sciences |
| Publication Year: |
2024 |
| Collection: |
University of Hong Kong: HKU Scholars Hub |
| Subject Terms: |
Accretion; Accretion disks; stars: neutron; X-rays: binaries; X-rays: general; X-rays: individuals: GX 5-1 |
| Description: |
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 3 σ 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. |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| Relation: |
Astronomy & Astrophysics; 15; WOS:001203444100003; https://hub.hku.hk/handle/10722/344004; 684 |
| DOI: |
10.1051/0004-6361/202347374 |
| Availability: |
https://hub.hku.hk/handle/10722/344004; https://doi.org/10.1051/0004-6361/202347374 |
| Rights: |
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. |
| Accession Number: |
edsbas.75F94A4B |
| Database: |
BASE |