Determination of mass of IGR J17091-3624 from "Spectro-Temporal" variations during onset-phase of the 2011 outburst

TL;DR

This study estimates the mass of black hole candidate IGR J17091-3624 during its 2011 outburst by analyzing spectral and temporal variations, using three methods and a joint likelihood approach, resulting in a mass range of approximately 8.7 to 15.6 solar masses.

Contribution

It introduces a combined mass estimation technique using multiple spectral and temporal analysis methods for black hole candidates.

Findings

Mass estimate range: 8.7 to 15.6 solar masses.

Probable mass range: 11.8 to 13.7 solar masses.

Methodology includes joint likelihood approach.

Abstract

The 2011 outburst of the black hole candidate IGR J17091-3624 followed the canonical track of state transitions along with the evolution of Quasi-Periodic Oscillation (QPO) frequencies before it began exhibiting various variability classes similar to GRS 1915+105. We use this canonical evolution of spectral and temporal properties to determine the mass of IGR J17091-3624, using three different methods, viz : Photon Index ($\Gamma$) - QPO frequency ($\nu$) correlation, QPO frequency ($\nu$) - Time (day) evolution and broadband spectral modelling based on Two Component Advective Flow. We provide a combined mass estimate for the source using a Naive Bayes based joint likelihood approach. This gives a probable mass range of 11.8 M$_{\odot}$ - 13.7 M$_{\odot}$. Considering each individual estimate and taking the lowermost and uppermost bounds among all three methods, we get a mass range of 8.7 M$_{\odot}$ - 15.6 M$_{\odot}$ with 90% confidence. We discuss the probable implications of our findings in the context of two component accretion flow.