X-ray polarimetry as a tool to measure the black hole spin in microquasars: simulations of IXPE capabilities

0570198 - ASÚ 2024 RIV GB eng J - Journal Article
Mikušincová, R. - Dovčiak, Michal - Bursa, Michal - Lalla, N. D. - Matt, G. - Svoboda, Jiří - Taverna, R. - Zhang, W.
X-ray polarimetry as a tool to measure the black hole spin in microquasars: simulations of IXPE capabilities.
Monthly Notices of the Royal Astronomical Society. Roč. 519, č. 4 (2023), s. 6138-6148. ISSN 0035-8711. E-ISSN 1365-2966
R&D Projects: GA ČR(CZ) GX21-06825X
Institutional support: RVO:67985815
Keywords : accretion discs * polarization * relativistic processes
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 4.8, year: 2022
Method of publishing: Limited access
https://doi.org/10.1093/mnras/stad077

We present simulated observations of an X-ray binary system with the Imaging X-ray Polarimetry Explorer (IXPE), with the aim to study the robustness of black hole spin and geometry measurements using X-ray polarimetry. As a representative example, we used the parameters of GRS 1915 + 105 in its former unobscured, soft state. In order to simulate the polarization properties, we modelled the source emission with a multicolour blackbody accounting for thermal radiation from the accretion disc, including returning radiation. Our analysis shows that the polarimetric observations in the X-ray waveband will be able to estimate both spin and inclination of the system with a good precision [without returning radiation we obtained for the lowest spin Delta a < 0.4 (0.4/0.998 similar to 40 per cent) for spin and Delta i < 30 degrees (30 degrees/70 degrees similar to 43 per cent) for inclination, while for the higher spin values we obtained Delta a < 0.12 ( similar to 12 per cent) for spin and Delta i < 20 degrees (similar to 29 per cent) for inclination, within 1 a errors]. When focusing on the case of returning radiation and treating inclination as a known parameter, we were able to successfully reconstruct spin and disc albedo in Delta a < 0.15 (similar to 15 per cent) interval and Delta albedo < 0.45 (45 per cent) intervals within 1 a errors. We conclude that X-ray polarimetry will be a useful tool to constrain black hole spins, in addition to timing and spectral-fitting methods.
Permanent Link: https://hdl.handle.net/11104/0341980