Supernovae without host galaxies? (P.-C. Zinn et al.)

Vol. 536
In section 4. Extragalactic astronomy

Supernovae without host galaxies? Hypervelocity stars in foreign galaxies

Hypervelocity stars (HVS) are stars that have been accelerated to velocities that are high enough to allow them to escape from their parent galaxy. The likely acceleration mechanism for most HVS is an interaction with the supermassive black hole in the galactic center. So far, hypervelocity stars have only been identified in our Galaxy, the Milky Way. They are too faint for direct detection in other galaxies with the possible exception of our nearest neighbors. However, many HVS will end their life in a supernova explosion. The authors have performed a systematic search of known supernovae without any obvious host galaxy. They carried out deep imaging around the supernova location to rule out faint low surface brightness galaxy hosts. Their search resulted in one candidate (SN 2006bx), which can be explained with good confidence as an HVS ejected from the parent galaxy UGC 5434.