Physical Society Colloquium

Observable Signatures of Merging Compact Binaries

Brian Metzger

Department of Astrophysical Sciences
Columbia University

Coalescing stellar mass compact objects (binary neutron stars [NSs] and blackholes) are promising sources for the direct detection of gravitational waves by Advanced LIGO and Virgo in the next few years. Maximizing the scientific return from such a discovery will require the identification of 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. NS 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 an in situ probe of an astrophysical site for the r-process. I will describe how free neutrons in the outermost layers of the ejecta power a bright precursor to the main kilonova emission, which could be diagnostic of the NS equation of state.