Compact Object Mergers

Binary compact object mergers are among the primary gravitational wave sources expected to be observed by the next generation of ground-based gravitational wave detectors. Mergers where one or both compact objects are neutron stars will further produce electromagnetic emission, and coincident observation of this together with gravitational wave emission could teach us much about the progenitor systems, test general relativity in the dynamical strong field regime, and help elucidate the nature of matter at nuclear density. I will begin by giving an overview of the state of the field. I will then discuss more recent work with collaborators focusing on mergers occurring while the orbit still has sizeable eccentricity, and where neutron stars are allowed to have rapid spins. Large eccentricity is expected for mergers that occur following dynamical capture or 3-body interactions in dense cluster environments, and observations imply millisecond pulsars are common in globular clusters. Though these events may be rarer than the traditional quasi-circular inspiral, they could exhibit strikingly different behavior, including zoom-whirl orbital dynamics, and large amounts of unbound material for cases where the neutron star is tidally disrupted. Neutron star spin also seems to provide an ingredient that can cause a hypermassive remnant formed in a binary neutron star merger to be susceptible to the so-called one-arm spiral instability.

Speaker: Frans Pretorius, Princeton