We report the results from \textit{ AstroSat} observations of the transient Galactic black hole X-ray binary MAXI J1535-571 during its hard-intermediate state of the 2017 outburst. We systematically study the individual and joint spectra from two simultaneously observing \textit{ AstroSat} X-ray instruments, and probe and measure a number of parameter values of accretion disc, corona and reflection from the disc in the system using models with generally increasing complexities. Using our broadband ($1.3-70$ keV) X-ray spectrum, we clearly show that a soft X-ray instrument, which works below $\sim 10-12$ keV, alone cannot correctly characterize the Comptonizing component from the corona, thus highlighting the importance of broadband spectral analysis. By fitting the reflection spectrum with the latest version of the \textsc{ relxill} family of relativistic reflection models, we constrain the black hole's dimensionless spin parameter to be $0.67^{ +0.16}_{ -0.04}$. We also jointly use the reflection spectral component (\textsc{ relxill}) and a general relativistic thin disc component (\texttt{ Kerrbb}), and estimate the black hole's mass and distance to be $10.39_{ -0.62}^{ +0.61} M_{ \odot}$ and $5.4_{ -1.1}^{ +1.8}$ kpc respectively.
Categories: astro-ph.HE hep-ex physics.data-an