Soft gamma-ray emission from the V404 Cygni outburst observed with INTEGRAL/PICsIT
P. Lubinski, A. Bazzano, L. Natalucci, P. Ubertini, M. Sobolewska, P. Zycki
V404 Cygni during its 2015 outburst was the brightest source ever observed by INTEGRAL in the soft gamma-ray band. This made possible to detect the source with the IBIS high energy detector PICsIT in many single pointings ($\approx$1 h long) allowing to study the evolution of the gamma-ray emission over the whole event period. In general, the PICsIT flux in the 255--340 keV band correlates with the hard X-ray flux measured by INTEGRAL/ISGRI, although we observe a saturation of the gamma-ray emission from the source. The spectra extracted for several short periods of the outburst were modelled with a Comptonization model. The plasma temperature remains stable despite a variation of the Compton parameter. We found a strong Compton reflection and a hint for a non-thermal emission occurring during some phases of the outburst. Our preliminary analysis do not show a presence of the positron annihilation line in the V404 Cygni spectra from the 2015 outburst.