Broadband Spectral Properties of MAXI J1348–630 using AstroSat Observations

Abstract

We present broadband X-ray spectral analysis of the black hole X-ray binary MAXI J1348–630, performed using five AstroSat observations. The source was in the soft spectral state for the first three observations and in the hard state for the last two. The three soft state spectra were modeled using a relativistic thin accretion disk with reflection features and thermal Comptonization. Joint fitting of the soft state spectra constrained the spin parameter of the black hole a * > 0.97 and the disk inclination angle i = degrees. The bright and faint hard states had bolometric flux a factor of ∼6 and ∼10 less than that of the soft state respectively. Their spectra were fitted using the same model except that the inner disk radius was not assumed to be at the last stable orbit. However, the estimated values do not indicate large truncation radii and the inferred accretion rate in the disk was an order of magnitude lower than that of the soft state. Along with earlier reported temporal analysis, AstroSat data provide a comprehensive picture of the evolution of the source.