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Astronomy Colloquium

Thursday, February 21, 2013
12:00 AM
Dennison 807

"Studying Massive Black Holes Using the Tidal Disruption of Stars"

A star that wanders too close to a massive black hole gets shredded by the black hole's tidal gravity. Stellar gas soon falls back to the black hole at a rate initially exceeding the Eddington rate, releasing a flare of energy as gas accretes.  How often this process occurs is uncertain at present, as is the physics of super-Eddington accretion (which is relevant for black hole growth and feedback at high redshift as well).  Excitingly, optical transient surveys like the Palomar Transient Factory (PTF), Pan-STARRS and LSST should be able to shed light on these questions soon.  To help these surveys find and interpret tidal disruption events, I predict their photometric and spectroscopic properties: Early on, much of the falling-back gas should blow away in a wind, producing luminous optical emission imprinted with blueshifted UV absorption lines.  In just the last couple of years, PTF, Pan-STARRS, and surprisingly the Swift hard X-ray satellite are, for the first time, finding and following up tidal disruption event candidates in real time.  I'll describe their recent discoveries in the context of our theoretical predictions, and also look to the future at what measured rates of tidal disruption will be able to teach us about massive black holes and their surrounding galactic nuclei.

Linda Strubbe, Canadian Institute for Theoretical Astrophysics (Toronto)