Accretion flow properties of GRS 1716-249 during its 2016–17 failed outburst

Abstract

In 2016–17, the Galactic transient black hole candidate GRS 1716-249 exhibited an outburst event after a long quiescence period of almost 23 years. The source remained in the outbursting phase for almost 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 spectral fit, we also estimate the probable mass of GRS 1716-249 to be in the range of 4.50 – 5.93 M⊙ or 5.01+0.92−0.51M⊙. Refitting of all spectra is done by freezing the mass at its average value. An insignificant deviation of the TCAF model parameters is observed. From the nature of the variation of the newly fitted spectral and temporal properties, we find that the source stays in only the harder (hard and hard-intermediate) states during the outburst. It does not make a transition to the softer states which makes it a ‘failed’ outburst.