Investigating the accretion and ejection physics of black hole X-ray binaries with spectroscopy and polarimetry: the case of GRS 1915+105

X-ray Polarimetry will open a new window in X-ray astronomy that can revolutionize the current understanding of the accretion and ejection mechanisms of black holes X-ray binaries (BHXBs). With the upcoming launch of the Imaging X-ray Polarimetry Explorer (IXPE) in 2021, X-ray astronomy will be benefited with the additional polarimetry signal along the currently existing timing and spectroscopic analysis. Since BHXBs are highly variable in time, the polarimetry signals might also vary depending upon various intrinsic properties. So, it is necessary to have a thorough spectral and timing analysis of different states of the source. We are currently performing a spectroscopic analysis of different states of GRS 1915+105. We find strong evidence of variability of the accretion disk wind in two soft/high and hard/low states using Chandra HETGS spectra, and we are investigating the origin of such variability using photo-ionization models and testing the MHD wind model recently employed for GRO J1655-40 (Fukumura et al 2017). We are also simulating the modulation factor and angle as to be seen by IXPE using the ixpeobssim simulator for the different states of GRS 1915+105. This work shows a promising case study for the future exploitation of X-ray spectroscopic and polarimetric signatures of black hole X-ray binaries to understand their accretion and ejection physics.