Confirmation of a highly relativistic transient jet launched from a supermassive black hole.

Tidal disruption events (TDEs) are transient, multi-wavelength events in which a star is ripped apart by a supermassive black hole. Observations show that in some fraction of TDEs, a short-lived, synchrotron emitting jet is produced. There has been ~5 events where this jet is pointed ~directly towards Earth. In this seminar I will present the results of the first 15 months of our radio/sub-mm observing campaign of the most recently discovered jetted TDE AT2022cmc. Our multi-frequency data set is centred around a high cadence light curve from the Arcminute Microkelvin Imager (AMI) which shows day timescale variability over the first 200 days. We attribute the variability to a very high brightness temperature emitting region, as opposed to scintillation. I will present a scenario in which the measured high brightness temperature is a result of relativistic beaming caused by a jet being launched at velocities close to the speed of light along our line of sight. I will also place our AMI light curve into a multi-frequency context and in the context of other radio-detected TDEs to demonstrate the importance of this event in terms of our understanding of supermassive black hole transients.