IXPE observation confirms a high spin in the accreting black hole 4U 1957+115

0586061 - ASÚ 2025 RIV FR eng J - Journal Article
Marra, L. - Brigitte, Maimouna - Cavero, N. R. - Dovčiak, Michal - Podgorný, Jakub - Svoboda, Jiří … Total 116 authors
IXPE observation confirms a high spin in the accreting black hole 4U 1957+115.
Astronomy & Astrophysics. Roč. 684, April (2024), č. článku A95. ISSN 0004-6361. E-ISSN 1432-0746
R&D Projects: GA ČR(CZ) GX21-06825X
Institutional support: RVO:67985815
Keywords : x-ray binary * accretion * accretion disks * black hole physics
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 6.5, year: 2022
Method of publishing: Open access

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 similar to 571 ks observation reveals a linear polarisation degree of 1.9% +/- 0.6% and a polarisation angle of41.(degrees)8 +/- 7.(degrees)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(degrees) are disfavoured.
Permanent Link: https://hdl.handle.net/11104/0354009