DOI

https://doi.org/10.48717/rbzz-ex18

Project

ED055

Title

ED055

Abstract

AT2019ijn is a luminous, fast optical transient with peculiar properties: it rises in less than 7 days and peaks with absolute magnitude between -18 and -25 (depending on the photometric redshift), while showing persistently blue color (g-r <~-0.13). It coincides with the center of a dwarf galaxy, although the current imaging sensitivity and resolution are not enough to be certain. Both its radio luminosity (>10^30 erg/s/Hz) and evolutional time-scale (peaks several hundred days after the optical discovery) are exceptional, differing from known transients of stellar origin. We request multi-frequency EVN observations to precisely localize the radio emission, and probe the radio structure at a milliarcsecond scale. If the jet were launched at the time of optical flare and the source is at z<0.25, EVN will be able to resolve the jet emission components, providing direct imaging evidence of a jetted FBOT. If the source remains unresolved, a higher redshift would be favored. In this case, EVN can establish a baseline position for future proper motion measurements. The EVN observations will also provide measurement of radio spectral slope which will help to diagnose the jet energetics and environment of this peculiar FBOT.