Accretion Flow Properties of GRS 1716-249 during its 2016-17 'failed' Outburst

TL;DR

This study analyzes the 2016-17 outburst of black hole candidate GRS 1716-249, revealing it remained in a hard state throughout, with spectral and temporal properties studied via multiple satellites and the TCAF model.

Contribution

The paper provides the first detailed spectral and temporal analysis of GRS 1716-249's failed outburst using the TCAF model, estimating the black hole's mass.

Findings

The source remained in the hard state during the entire outburst.

No transition to softer spectral states was observed.

Estimated black hole mass is between 4.50 and 5.93 solar masses.

Abstract

In $2016-17$, the Galactic transient black hole candidate GRS 1716-249 exhibited an outburst event after a long period of quiescence of almost 23 years. The source remained in the outbursting phase for $\sim 9$ months. We study the spectral and temporal properties of the source during this outburst using archival data from four astronomy satellites, namely MAXI, Swift, NuSTAR and AstroSat. Initial spectral analysis is done using combined disk black body and power-law models. For a better understanding of the accretion flow properties, we studied spectra with the physical two component advective flow (TCAF) model. Accretion flow parameters are extracted directly from the spectral fits with the TCAF model. Low frequency quasi-periodic oscillations are also observed in the Swift/XRT and AstroSat/LAXPC data. From the nature of the variation of the spectral and temporal properties, we find the source remains in hard state during the entire outburst. It never had a transition to other states which makes this event a `failed' outburst. An absence of the softer spectral states is consistent with the class of short orbital period objects, where the source belongs to. From the spectral fit, we also estimate the probable mass of GRS~1716-249 to be in the range of $4.50-5.93 M_\odot$ or $5.02^{+0.91}_{-0.52} M_\odot$.