P. Atri

TL;DR: In this paper, radio and X-ray monitoring over ≈ 3 months of the renewed activity to study the coupling between the jet and the inner regions of the disk/jet system was presented.

TL;DR: In this paper , the authors presented rapid follow-up radio observations of the exceptionally bright gamma-ray burst GRB 221009A that reveal in detail, both temporally and in frequency space, an optically thick rising component from the reverse shock.

TL;DR: In this paper, the authors present extremely deep upper limits on the radio emission from 4U~1957+11, an X-ray binary that is generally believed to be a persistently accreting black hole that is almost always in the soft state.

Abstract: We present the spectral and timing analysis of X-ray observations performed on the Galactic black hole transient GRS 1716-249 during the 2016-2017 outburst. The source was almost continuously observed with the Neil Gehrels Swift Observatory from December 2016 until October 2017. The X-ray hardness ratio and timing evolution indicate that the source approached the soft state three times during the outburst, even though it never reached the canonical soft spectral state. Thus, GRS 1716-249 increases the number of black hole transients showing outbursts with "failed" state transition. During the softening events, XRT and BAT broadband spectral modeling, performed with thermal Comptonization plus a multicolor disc black-body, showed a photon index (Gamma 10%). We find that, coherently with a scenario in which the disc moves closer to the compact object, the accretion disc inner radius decreases with the increase of the inner disc temperature, until a certain point when the temperature starts to increase at constant radius. This, in addition with the spectral analysis results, suggests that either the accretion disc reached the innermost stable circular orbit during the hard intermediate state or the hot accretion flow might re-condensate in an inner mini-disc. We report on the radio observations performed during the outburst finding that GRS 1716-249 is located on the radio-quiet "outlier" branch of the radio/X-ray luminosity plane.