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INTEGRAL and ATCA observations of the black hole transient GRS 1716-249

ATel #10069; Melania Del Santo (INAF/IASF-Palermo, Italy), Lorenzo Ducci (IAAT, Germany; ISDC, Switzerland), James Miller-Jones (ICRAR-Curtin, Australia), Carlo Ferrigno (ISDC, Switzerland), Antonino D'Ai' (INAF/IASF-Palermo, Italy), Tiziana Bassi (INAF/IASF-Palermo, Universita' di Palermo, Italy), Simone Migliari (ESA Madrid, Spain), John Tomsick (SSL/UCB, USA), Piergiorgio Casella (INAF/OAR, Italy), Tomaso Belloni (INAF/OAB, Italy), Greg Sivakoff (University of Alberta, Canada)
on 11 Feb 2017; 13:41 UT
Credential Certification: Melania Del Santo (melania@ifc.inaf.it)

Subjects: Black Hole, Transient

Referred to by ATel #: 10196, 10236

INTEGRAL performed a target of opportunity observation of the black-hole X-ray transient GRS 1716-249 during the on-going outburst (ATel #9876, #9895). The 90 ks observation started on 2017 February 8th at 22:37:54 and ended on February 10th at 00:52:56 (UTC).
The source flux was more than 0.5 Crab in the 20-80 keV band covered by the IBIS/ISGRI detector and 0.3 Crab in the 3-20 keV, as determined using JEM-X. The source emission extends significantly up to 300 keV. Preliminary spectral analysis shows a hard spectrum well modelled with a cutoff power-law (CUTOFFPL in XSPEC) with gamma=1.66+/-0.05 and a roll-over at very high energy, i.e. about 240 keV. We also fit the broad-band spectrum with NTHCOMP obtaining a power-law slope of 1.73+/-0.03 and the Comptonising electron temperature kTe=165+124/-48 keV. The 0.1-500 keV flux, which is 2.8E-8 erg/cm^2/s is consistent with the Swift flux observed at the end of January (ATel #10036).
A combined radio observation was performed on 2017 February 9th from 19:00 to 21:00 UT with the Australia Telescope Compact Array under NAPA program C2538, for a total of 80 min of on-source exposure time. A radio source is clearly detected at the target position. Preliminary analysis shows that an elliptical Gaussian fit to the source in the image plane gives a 5.5-GHz flux density of 3.28+/-0.05 mJy/beam.
We note that the X-ray spectral slope and radio detection are consistent with a hard spectral state, although the high-energy cutoff, as well as the electron temperature, are quite high.
Further simultaneous observations with REM and Swift have been performed and the analysis is on-going.
We would like to thank the INTEGRAL Project Scientist and the science planners and the ATCA schedulers for making these observations possible.