Program: GN-2021A-DD-101

We request 2 hours of Gemini N/NIRI J and Ks-band imaging at the location of a red supergiant star in M51 that has vanished, potentially as a 'failed supernova' that directly collapsed into a black hole. There is mounting evidence, both observational and theoretical, that 10-30% of core collapses do not yield a supernova explosion, but only one viable candidate for such a 'failed supernova' event has been observed thus far. Here we have discovered a new, strong candidate for the disappearance of a luminous star in M51 which has been detected dozens of times with HST through late 2017. The star had the characteristics of a 25-30 M_sun red supergiant before it faded from view (>2.0 mag) in 2019 in a crowded region of a spiral arm. Deep near-IR imaging with Gemini will confirm the nature of the vanished star and rule out possible alternatives, such as a surviving dust-obscured star. Depending on the results, this will be a prime target for continued monitoring with HST, JWST, and Chandra. Confirmation of a second strong case for a 'failed supernova' will have broad consequences, not only for verifying this channel of stellar death, but for our understanding of stellar remnants, chemical enrichment, and ultimately models of black hole formation.