The Long Outburst of the Black Hole Transient GRS 1716-249

Abstract

We report on the multi-frequency study of the black hole transient GRS 1716-249 during the 2016-2017 outburst, after 23 years in quiescence. GRS 1716-249 was observed with the Neil Gehrels Swift Observatory from December 2016 until October 2017. In addition we triggered an INTEGRAL ToO combined with radio and infrared observations during the hard spectral state of the source. We have analysed all XRT and BAT data available. The X-ray hardness ratio and timing evolution indicate that the source spectrum became softer three times during the outburst. During these events, the broad band spectral modeling, performed with a thermal Comptonization plus a multicolor disk blackbody, showed spectral parameters characteristic of the hard intermediate state, also in agreement with the root mean square amplitude of the flux variability. Moreover, we present preliminary results of the spectral energy distribution modeling of GRS 1716-249 in the framework of the compact jet internal shock model.