Accretion Properties of MAXI J1813-095 during its Failed Outburst in 2018

TL;DR

This study analyzes the 2018 failed outburst of the black hole candidate MAXI J1813-095 using multi-instrument observations, revealing it remained in the hard state, with estimates of black hole mass, spin, and system inclination.

Contribution

First detailed timing and spectral analysis of MAXI J1813-095 during its failed outburst, including physical modeling with TCAF and reflection models to estimate key system parameters.

Findings

Source remained in the hard state during the entire outburst.

Black hole mass estimated at 7.4 ± 1.5 solar masses.

Black hole spin parameter estimated as > 0.76.

Abstract

We present the results obtained from detailed timing and spectral studies of a black hole candidate MAXI~J1813-095 using {\it Swift}, {\it NICER}, and {\it NuSTAR} observations during its 2018 outburst. The timing behaviour of the source is mainly studied by using {\it NICER} light curves in a $0.5-10$ keV range. We did not find any signature of quasi-periodic oscillations in the power density spectra of the source. We carry out spectral analysis with a combined disk blackbody \& power-law model, and a physical two-component advective flow (TCAF) model. From the combined {\tt disk blackbody} \& {\tt power-law} model, we extracted thermal and non-thermal fluxes, photon index, and inner disk temperature. We also find evidence for weak reflection in the spectra. We have tested the physical TCAF model on a broadband spectrum from {\it NuSTAR} and {\it Swift}/XRT. The parameters like mass accretion rates, the size of the Compton clouds and the shock strength are extracted. Our result shows that the source remained in the hard state during the entire outburst which indicates a `failed' outburst. We estimate the mass of the black hole as $7.4 \pm 1.5$ $M_{\odot}$ from the spectral study with the TCAF model. We use {\tt LAOR} model for the Fe K$\alpha$ line emission. From this, the spin parameter of the black hole is estimated as $a^* > 0.76$. The inclination angle of the system is estimated to be in the range of $28^{\circ} - 45^{\circ}$ from the reflection model. We estimate the source distance to be $\sim 6$ kpc.