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.