Matt Kistler homepage. Matthew Kistler A High Rate of White Dwarf-Neutron Star Mergers & Their Transients
Are white dwarfs merging with neutron stars (or black holes) at a higher rate than we thought?
Recently, a close binary system consisting of a white dwarf and a neutron star (or possibly a black hole) was discovered (in Sloan Digital Sky Survey data) to be at a distance of only ~50 pc, with a timescale for merging of only ~500 Myr. In this paper with Todd Thompson and Kris Stanek, we argue that this groundbreaking discovery implies that such systems are common, with of order 1 million in the Milky Way. Although subject to large uncertainties, the rate of merger events derived from such objects is ~5 x 10^-4 per yr in the Galaxy, just ~3-6 and ~20-40 times less than the Type Ia and core-collapse supernova (SN) rates, respectively. This merger rate is ~5000-10000 times more than the observed (beaming-uncorrected) rate of long-duration gamma-ray bursts. We discuss a number of implications for the census of both long and short GRBs and their progenitors, the origin of ultrahigh-energy cosmic rays, the formation of rapidly rotating neutron stars and ~2-3 solar mass black holes, the population of pulsars in the Galaxy, as well as for upcoming and current transient surveys and for high- (LIGO) and low-frequency (LISA) gravitational wave searches.
