Signatures of Neutron Star Mergers in the Era of Advanced LIGO

Coalescing stellar mass compact objects (binary neutron stars and black holes) are promising sources for the direct detection of gravitational waves by Advanced LIGO in the next few years, if not this fall. Maximizing the scientific return from such a discovery will require identifying a coincident electromagnetic counterpart.  One possible counterpart is a short gamma ray burst, powered by the accretion of a centrifugally supported torus onto the central black hole.  Neutron star mergers are also accompanied by a thermal optical/IR transient, powered by the radioactive decay of neutron-rich elements synthesized in the merger ejecta (a `kilonova').  In addition to providing a beacon to the gravitational wave chirp, kilonovae provide a direct probe of an astrophysical site for rapid neutron capture (r-process) nucleosynthesis.  I will describe recent work showing how free neutrons in the outermost layers of the ejecta could power a bright 'precursor' to the main kilonova emission, greatly enhancing the prospects for its detection.

Speaker: Brian Metzger, Columbia University