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

Observing the x-ray black hole binary source GRS1915+105 has been classified as a top priority during the first year of IXPE operation. The primarily occurrence of the source in thermal state makes it the perfect candidate for black hole spin measurements. To credibly assess the source polarimetric properties, we use a multicolor black body emission model accounting for thermal radiation from the disk accretion complemented by self-irradiation of the accretion disk. We simulate the future observations of GRS1915+105 with IXPE and study the impact of a constant albedo on the polarization properties of the source. We demonstrate the capabilities of the mission and the precision of the black hole spin constraints. GRS1915+105 has been in an obscured state since 2018, and is therefore used as a test source in this study. However, the results obtained from our analysis are applicable to any bright source in thermal state.