On August 17, 2017, a new era of astronomy was inaugurated by a short gamma-ray burst accompanying the gravitational wave GW170817 detected by LIGO-VIRGO.  While the neutrinos from SN1987a had been a first milestone towards multi-messenger astronomy three decades earlier, the true breakthrough in High-Energy Neutrino astronomy is about to take place today, due to the recent advances in large volume ice and water detectors.

One of the most important observational challenges of our time is to establish the link between the discoveries of these new astronomies and the electromagnetic Universe. As the same violent phenomena that generate gravitational waves and/or high energy neutrinos are also the source of high energy photons, gamma-ray astronomy has been – and will remain – pivotal in connecting new and “old” astronomies.

Besides leading an ambitious legacy science program, INTEGRAL is presently one of the best suited detectors for identifying electromagnetic counterparts to the cataclysmic events that will continue to be discovered with gravitational waves and high energy neutrinos. This conference will discuss recent developments in high energy astronomy, with particular emphasis on its role in multi-messenger astronomy. Beyond the present generation of gamma-ray instruments, the choral of multi-messenger astronomies will require a voice in the MeV band. One of the aims of the workshop is therefore to review the status and development of future instruments and to discuss perspectives in observational gamma-ray astronomy; these topics will be highlighted during the meeting as AHEAD Gamma-ray workshop (AHEAD is a European Community H2020 program, one of its goals is enabling the development of future gamma-ray astrophysics missions).