Disruption of a Red Giant Star by a Supermassive Black Hole and the Case
  of PS1-10jh
  The development of a new generation of theoretical models for tidal
disruptions is timely, as increasingly diverse events are being captured in
surveys of the transient sky. Recently, Gezari et al. reported a discovery of a
new class of tidal disruption events: the disruption of a helium-rich stellar
core, thought to be a remnant of a red giant (RG) star. Motivated by this
discovery and in anticipation of others, we consider tidal interaction of an RG
star with a supermassive black hole (SMBH) which leads to the stripping of the
stellar envelope and subsequent inspiral of the compact core toward the black
hole. Once the stellar envelope is removed the inspiral of the core is driven
by tidal heating as well as the emission of gravitational radiation until the
core either falls into the SMBH or is tidally disrupted. In the case of tidal
disruption candidate PS1-10jh we find that there is a set of orbital solutions
at high eccentricities in which the tidally stripped hydrogen envelope is
accreted by the SMBH before the helium core is disrupted. This places the RG
core in a portion of parameter space where strong tidal heating can lift the
degeneracy of the compact remnant and disrupt it before it reaches the tidal
radius. We consider how this sequence of events explains the puzzling absence
of the hydrogen emission lines from the spectrum of PS1-10jh and gives rise to
its other observational features.
