2017 June 12
2017 August 23
Hard X-ray spectra of black hole binaries are produced by the inverse Comptonization of soft seed photons by hot electrons near the black hole. The slope of the resulting energy spectra is governed by two main parameters: the electron temperature and the optical depth of the emitting plasma. The extremely bright outburst of V404 Cyg in June 2015, provides a unique data set to perform time resolved spectroscopy and study in detail the evolution of the parameters describing the Comptonizing plasma. We present here the results of IBIS/ISGRI spectral analysis in the 20-200 keV energy range over the period 18-28 June 2015.