Marra et al.;
(2024)
IXPE observation confirms a high spin in the accreting black hole 4U 1957+115.
Astronomy & Astrophysics (A&A)
, 684
, Article A95. 10.1051/0004-6361/202348277.
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Abstract
We present the results of the first X-ray polarimetric observation of the low-mass X-ray binary 4U 1957+115, performed with the Imaging X-ray Polarimetry Explorer in May 2023. The binary system has been in a high-soft spectral state since its discovery and is thought to host a black hole. The ∼571 ks observation reveals a linear polarisation degree of 1.9%±0.6% and a polarisation angle of −41.°8±7.°9 in the 2–8 keV energy range. Spectral modelling is consistent with the dominant contribution coming from the standard accretion disc, while polarimetric data suggest a significant role of returning radiation: photons that are bent by strong gravity effects and forced to return to the disc surface, where they can be reflected before eventually reaching the observer. In this setting, we find that models with a black hole spin lower than 0.96 and an inclination lower than 50° are disfavoured.
| Type: | Article |
|---|---|
| Title: | IXPE observation confirms a high spin in the accreting black hole 4U 1957+115 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1051/0004-6361/202348277 |
| Publisher version: | https://doi.org/10.1051/0004-6361/202348277 |
| Language: | English |
| Additional information: | Copyright © The Authors 2024. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication. |
| Keywords: | Accretion / accretion disks / black hole physics / polarization / X-rays: binaries / X-rays: individuals: 4U 1957+115 |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10179200 |
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