Self-Consistent Disk-Reflection Analysis of the Black-Hole Candidate X-ray Binary MAXI J1813-095 with NICER, Swift, Chandra, and NuSTAR

TL;DR

This study analyzes the black-hole candidate MAXI J1813-095 during its 2018 outburst using multi-instrument X-ray data, revealing a relativistic iron line, a possibly truncated disk, and a high reflection fraction, advancing understanding of accretion physics.

Contribution

It introduces a self-consistent spectral modeling approach coupling disk, Comptonization, and reflection components, with a focus on the reflection fraction and disk geometry in MAXI J1813-095.

Findings

Relativistic iron line detected at ~6.5 keV.

Inner disk radius estimated at ~2 Rg, consistent with a slightly truncated disk.

Reflection fraction found to be of order unity, higher than previous estimates.

Abstract

We present our analysis of MAXI J1813-095 during its hard state ``stalled'' outburst in 2018. This self-consistent analysis has been carried out using \NICER, \Swift, \Chandra, and {\NuSTAR} throughout seven observations of MAXI J1813-095. We find a relativistic iron line at $\sim$6.5 keV from the inner region of the accretion disk. Our results are consistent with a slightly truncated disk or non-truncated disk for an inner radius of $\sim$2$R_\mathrm{g}$ and minimum spin of $>$0.7 with a best value of $\sim0.9$, assuming $R_\mathrm{in}$ reaches the innermost stable circular orbit at $\it{L_\mathrm{x}}$ $\sim$ 1\% $\it{L_\mathrm{Edd}}$. We analyzed MAXI J1813-095 over its outburst employing a spectral model which self-consistently couples the seed disk photons to the Comptonization and reflection components, also inclusive of reflection Comptonization. The unique aspect of this work is a reflection fraction of order unity, which is significantly higher than previous studies of this source, and is a consequence of applying the self-consistent disk-Comptonization-reflection spectral model. Other key parameters such as inclination and inner radius are found to be consistent with other works. works.