Abstract for Proposal 090357

XMM-Newton follow-up of electromagnetic counterparts to GW triggers during LVKC-

The joint detection of GWs and light from the NS merger GW170817 ushered us into a new era. Deep X-ray observations of GW170817 over 4 yr constrained the structural properties of a relativistic outflow launched by an NS merger and possibly detected the first evidence for the emerging kilonova afterglow. After this landmark discovery, the frontier is now to map the properties of a population of GW sources. We propose to exploit the unique capabilities of XMM-Newton to constrain the broad-band properties of 2 GW sources detected during LVKC-O4. Our immediate goals are: (i) map the diversity of emission from NS mergers, (ii) test the nature of the remnant object, (iii) determine if all mergers launch a jet, (iv) enable the first X-ray detections of NS-BH mergers or unclassified GW sources.

Details on Observing Strategy and Trigger Criteria
The observing trigger can come from a variety of instruments at different wavelengths: - high energy instruments with a relatively good positional accuracy of a few armin2 (Swift/BAT, INTEGRAL, Fermi/LAT, MAXI, AGILE); - soft X-ray instruments like Swift/XRT; - optical/NIR counterpart from wide-field surveys and/or targeted searches (only if a firm candidate is available). Reaction time is as fast as possible for the first activation. EPIC in full-frame thin filter. OM in fast timing with u filter. For later observations, the trigger can come from any well-identified GW-EM counterpart.