Abstract for Proposal 087200

Identifying and Characterizing X- and Gamma-ray Counterparts of Gravitational Wave Sources with INTEGRAL and XMM-Newton

During the O2 LIGO/Virgo run of last year the first electromagnetic counterpart to a gravitational wave (GW) source was detected.INTEGRAL played a key role by detecting the prompt gamma-ray emission associated with it. INTEGRAL also carried out searches for delayed emission from this and other GW sources, providing the deepest upper limits to date in the hard X-ray and gamma-ray bands. Despite no official Ligo/Virgo science run is foreseen in 2021, we propose a series of ToO Observations to follow-up the GW alerts during the next INTEGRAL AO period in order to cover potential triggers produced during engineering runs especially of the newly built Japanese KAGRA interferometer. Our strategy is twofold: first we propose to quickly scan the GW error box with INTEGRAL in order to find the hard X-ray counterpart of GW alerts, secondly, we propose longer term observations of any X-ray detected counterpart (even if not discovered by INTEGRAL) with INTEGRAL and XMM.

Details on Observing Strategy and Trigger Criteria

We propose to follow-up with INTEGRAL six GW alerts. In case of identification of an electromagnetic counterpart from any of the above sources, we ask for INTEGRAL follow-up observations lasting three orbits. To support and complete these follow-up observations we ask for a total of four 20 ks of simultaneous XMM-Newton observations either to be used on the same source to monitor its behaviour over time or to be spent in different counterparts during the O3 run 2.