Broadband reflection spectroscopy of MAXI J1535-571 using AstroSat: Estimation of black hole mass and spin

Abstract

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 $0.67_{-0.04}^{+0.16}$. 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.

Accepted for publication in MNRAS

References in corpus (3)

• The role of the reflection fraction in constraining black hole spin
• Large Area X-ray Proportional Counter (LAXPC) Instrument on AstroSat and Some Preliminary Results from its performance in the orbit
• Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR

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• Spectro-timing analysis of MAXI J1535-571 using AstroSat
• A NICER look at the state transitions of the black hole candidate MAXI J1535-571 during its reflares
• A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR
• Broadband X-ray analysis of 1E 1740.7-2942: constraints on spin, inclination and a tentative black hole mass