Tidal disruption flares of stars from moderately recoiled black holes

Abstract

We analyse stellar tidal disruption events as a possible observational signature of gravitational wave induced recoil of supermassive black holes. As a black hole wanders through its galaxy, it will tidally disrupt bound and unbound stars at rates potentially observable by upcoming optical transient surveys. To quantify these rates, we explore a broad range of host galaxy and black hole kick parameters. We find that emission from a transient accretion disc can produce similar to 1 event per year which the Large Synoptic Survey Telescope would identify as spatially offset, while super-Eddington outflows, if they exist, are likely to produce similar to 10 spatially offset events per year. A majority of tidal disruption flares, and a large majority of flares with an observable spatial offset, are due to bound rather than unbound stars. The total number of disruption events due to recoiled black holes could be almost 1 per cent of the total stellar tidal disruption rate.