A New Class of X-ray Transients? Highly Luminous XMM Transients

Finding X-ray counterparts to future LIGO/Virgo events requires an understanding of the transient sky at low redshift. We have identified 7 nearby (D < 300 Mpc) transients in the XMM-Newton Slew Survey Catalog via a systematic comparison with the ROSAT All Sky Survey. These sources have unusual properties and so are difficult to characterize. They are highly luminous (>1e42 erg/s), extremely variable, associated with galaxies within 300 Mpc, and lack optical AGN signatures. We propose to observe these seven targets with XMM-Newton in an attempt to identify their nature. The sources could prove to be tidal disruption events, GRB afterglows, very high energy ULXs, or some new class. This is the first study of X-ray transients within the LIGO/Virgo horizon.