Maximum speed of hypervelocity stars ejected from binaries

Abstract

The recent detection of hypervelocity stars (HVSs) as late-type B-stars and HVS candidateG/K dwarfs raises the important question of their origin. In this Letter, we investigate the maximum possible velocities of such HVSs if they are produced from binaries which are disrupted via an asymmetric supernova explosion. We find that HVSs up to ~770 and ~1280 km s-1 are possible in the Galactic rest frame from this scenario for these two subclasses of HVSs, respectively. We conclude that whereas a binary origin cannot easily explain all of the observed velocities of B-type HVSs (in agreement with their proposed centralmassive black hole origin) it can indeed account for the far majority (if not all) of the recently detected G/K-dwarf HVS candidates.