The first X-ray polarimetric observation of the black hole binary LMC X-1

0582159 - ASÚ 2024 RIV US eng J - Journal Article
Podgorný, Jakub - Marra, L. - Muleri, F. - Dovčiak, Michal - Brigitte, Maimouna - Svoboda, Jiří - Karas, Vladimír … Total 111 authors
The first X-ray polarimetric observation of the black hole binary LMC X-1.
Monthly Notices of the Royal Astronomical Society. Roč. 526, č. 4 (2023), s. 5964-5975. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GX21-06825X
Institutional support: RVO:67985815
Keywords : accretion discs * black hole physics * polarization
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.8, year: 2022
Method of publishing: Open access

We report on an X-ray polarimetric observation of the high-mass X-ray binary LMC X-1 in the high/soft state, obtained by the Imaging X-ray Polarimetry Explorer (IXPE) in 2022 October. The measured polarization is below the minimum detectable polarization of 1.1 per cent (at the 99 per cent confidence level). Simultaneously, the source was observed with the Neutron Star Interior Composition Explorer (NICER), Nuclear Spectroscopic Telescope Array (NuSTAR), and Spectrum-Rontgen-Gamma (SRG)/Astronomical Roentgen Telescope - X-ray Concentrator (ART-XC) instruments, which enabled spectral decomposition into a dominant thermal component and a Comptonized one. The low 2-8 keV polarization of the source did not allow for strong constraints on the black hole spin and inclination of the accretion disc. However, if the orbital inclination of about 36° is assumed, then the upper limit is consistent with predictions for pure thermal emission from geometrically thin and optically thick discs. Assuming the polarization degree of the Comptonization component to be 0, 4, or 10 per cent, and oriented perpendicular to the polarization of the disc emission (in turn assumed to be perpendicular to the large-scale ionization cone orientation detected in the optical band), an upper limit to the polarization of the disc emission of 1.0, 0.9, or 0.9 per cent, respectively, is found (at the 99 per cent confidence level).

Permanent Link: https://hdl.handle.net/11104/0350230