Brian Metzger
Columbia University

A Zoo of Tidal Disruption Flares

Occasionally a star in a galactic nucleus is perturbed onto a highly eccentric orbit that brings it close enough to the central supermassive black hole (BH) to be torn apart by tidal forces. Rapid accretion of stellar debris following such a tidal disruption event (TDE) has long been predicted to power a luminous electromagnetic flare, detectable to cosmological distances. I will review the basic theory of TDEs and recent observations of TDE flares. I will describe a highly simplified model for their thermal (optical, soft X-ray) emission based on the assumption that only a small fraction f_in << 1 of the initially bound stellar debris is ultimated accreted by the BH, with the vast majority f_out ~ 1-f_in ~ 1 instead ejected in a slow outflow. In addition to thermal emission, a small fraction of TDEs are observed to produce relativistic jets and bright non-thermal emission. I will describe numerical simulations of the deceleration of TDE jets, which indicate a complex jet angular structure. I will highlight several TDE “rate crises”, namely that the total predicted TDE rate >> observed thermal flare rate >> jetted TDE rate.