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<b>High Energy-Astrophysics</b><br><i>Observational Signatures of Neutron Star Mergers'</i>

Monday, November 29, 2010
12:00 AM
335 West Hall

Speaker: Brian Metzger (Princeton)

A fraction of neutron star (NS) and black hole binaries are formed sufficiently compact that they in-spiral and merge due to the emission of gravitational waves within the lifetime of the Universe. Such compact object mergers are among the most promising sources for the direct detection of gravitational waves with ground-based interferometers such as LIGO and Virgo. Maximizing the science of such a detection will, however, require identifying a coincident electromagnetic (EM) counterpart. One possible source of EM emission is a gamma-ray burst (GRB), powered by the accretion of material that remains in a rotationally-supported torus around the central black hole. I will overview the observational and theoretical status of the connection between NS mergers and the "short duration" subclass of GRBs. Although new observations from NASA's Swift observatory have provided some evidence in favor of the merger model, the puzzling discovery has also been made that many short GRBs are followed by late-time X-ray flaring activity, which does not fit current theory and may require modifying or considering alternative progenitor models. Another source of EM emission from NS mergers is a supernova-like optical transient, powered by the radioactive decay of heavy elements synthesized in neutron-rich ejecta from the merger. I will present the first calculations of the radioactively-powered transients from mergers that include both realistic nuclear physics and radiative transport, and I will discuss the prospects for detecting and identifying such events with present and future telescopes.