estimating the spin of MAXI J1348--630 from intermediate and soft states using \textit{Insight}-HXMT data

TL;DR

This study estimates the black hole spin in MAXI J1348--630 during its 2019 outburst using broadband spectral analysis with Insight-HXMT data, combining reflection and continuum fitting methods.

Contribution

It provides a new measurement of the black hole's spin and explores systematic uncertainties affecting spin determination in this source.

Findings

Black hole spin estimated at a=0.79±0.13.

High disc density (~10^{22} cm^{-3}) observed.

Moderate iron abundance (~2.5 times solar).

Abstract

We present a broadband spectral analysis of the soft-intermediate and soft states using \textit{Insight}-HXMT observations of the black hole binary MAXI J1348--630 during its outburst in 2019. We employ a combination of reflection and continuum fitting methods to measure the spin of the black hole and determine a spin of $a=0.79\pm0.13$, which is consistent with most of the previous results. Additionally, we investigate some sources of systematic uncertainty that could bias the measurement. The valid spectral hardening factor can partially account for the spin evolution observed during the outburst. Other potential factors, such as assumptions about the corona's structure and their interaction with reflected photons, can also affect the accuracy of spin measurements. Furthermore, our analysis reveals that MAXI J1348--630 exhibits a significantly high disc density ($\sim10^{22}\,\rm{cm}^{-3}$), with a moderate iron abundance of approximately 2.5 times solar.