LAUSR

Description Radio evidence of a stellar merger Core collapse supernovae occur when a massive star exhausts its fuel and explodes. Theorists have predicted that a similar explosion could occur if an evolved massive star merges with a compact companion, such as a neutron star. Dong et al. have identified a radio source that was not present in earlier radio surveys. Follow-up radio and optical spectroscopy show that it is an expanding supernova remnant slamming into surrounding material, probably ejected from the star centuries before it exploded. An unidentified x-ray transient occurred at a consistent location in 2014, suggesting an explosion at that time that produced a jet. The authors suggest that the most likely explanation is a merger-triggered supernova. —KTS A transient astronomical radio source indicates a supernova triggered by a merger between a star and a compact object. A core collapse supernova occurs when exothermic fusion ceases in the core of a massive star, which is typically caused by exhaustion of nuclear fuel. Theory predicts that fusion could be interrupted earlier by merging of the star with a compact binary companion. We report a luminous radio transient, VT J121001+495647, found in the Very Large Array Sky Survey. The radio emission is consistent with supernova ejecta colliding with a dense shell of material, potentially ejected by binary interaction in the centuries before explosion. We associate the supernova with an archival x-ray transient, which implies that a relativistic jet was launched during the explosion. The combination of an early relativistic jet and late-time dense interaction is consistent with expectations for a merger-driven explosion.