The spin measurement of the black hole SLX 1746-331 using Insight-HXMT observations

Abstract

We present an X-ray spectral analysis of a black hole X-ray binary SLX 1746-331 during the 2023 outburst using five \textit{Insight}-HXMT observations. We jointly use the reflection model \texttt{relxillcp} and the general relativistic thermal thin disk model \texttt{kerrbb} to fit the spectra from 2 - 100 keV. By jointly fitting the five spectra, we constrained the black hole mass to be $M=5.8\pm 0.3M_{\odot }$ and dimensionless spin parameter to be $a_{\ast }=0.88_{-0.02}^{+0.01}$ (90 percent statistical confidence). The reflection model shows that SLX 1746-331 is a high-inclination system with the inclination angle $i=63.7_{-1.0}^{+1.3}$ degrees, the accretion disk has a density $\log \mathrm{N}\sim 16\mathrm{c}{\mathrm{m}}^{-3}$. In addition, with the different reflection model \texttt{relxilllp}, which assumes a lamp-post geometry corona, we still give similar results.

9 pages, 5 figures and 4 tables, ApJ in press