Abstract:

The VLA Sky Survey (VLASS) is mapping > 80% of the GHz radio sky over multiple epochs, providing a 100x increase in the volume available for blind radio transient searches. In this volume, we have identified >1000 sources that are present in one epoch of VLASS but absent from either a previous VLASS epoch or a comparable historical radio sky survey. Through a combination of contextual clues and follow-up observations, we are often able to extract rich information on the nature of these transients. 

One notable example is VT J121001+495647: an unusually radio-luminous transient located in an off-nuclear region of a dwarf star forming galaxy. The late-time radio and optical spectra of this source are consistent with supernova ejecta shocking a dense extended circumstellar shell, likely ejected via binary interaction in the centuries leading to explosion. An associated archival X-ray transient indicates the launch of a relativistic jet at the time of explosion. This combination of an early jet and late-time interaction is consistent with theoretical models of a core collapse supernova triggered by the merger of a compact object with its massive binary companion. Together, these observations provide evidence for a new endpoint in the evolution of stellar binaries.