Possible Origin of the G2 Cloud from the Tidal Disruption of a Known
  Giant Star by Sgr A*
  The discovery of the gas cloud G2 on a near-radial orbit about Sgr A* has
prompted much speculation on its origin. In this Letter, we propose that G2
formed out of the debris stream produced by the removal of mass from the outer
envelope of a nearby giant star. We perform hydrodynamical simulations of the
returning tidal debris stream with cooling, and find that the stream condenses
into clumps that fall periodically onto Sgr A*. We propose that one of these
clumps is the observed G2 cloud, with the rest of the stream being detectable
at lower Br-$\gamma$ emissivity along a trajectory that would trace from G2 to
the star that was partially disrupted. By simultaneously fitting the orbits of
S2, G2, and $\sim$ 2,000 candidate stars, and by fixing the orbital plane of
each candidate star to G2 (as is expected for a tidal disruption), we find that
several stars have orbits that are compatible with the notion that one of them
was tidally disrupted to produce G2. If one of these stars were indeed
disrupted, it last encountered Sgr A* hundreds of years ago, and has likely
encountered Sgr A* repeatedly. However, while these stars are compatible with
the giant disruption scenario given their measured positions and proper
motions, their radial velocities are currently unknown. If one of these stars'
radial velocity is measured to be compatible with a disruptive orbit, it would
strongly suggest its disruption produced G2.
