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arXiv · 0912.0009

A High Rate of White Dwarf-Neutron Star Mergers & Their Transients

Todd A. Thompson·Matthew D. Kistler·K. Z. Stanek
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Abstract

We argue that the recent groundbreaking discovery by Badenes et al. (2009) of a nearby (~50 pc) white dwarf-neutron star (or black hole) binary (SDSS 1257+5428) with a merger timescale ~500 Myr implies that such systems are common; we estimate that there are of order 10^6 in the Galaxy. Although subject to large uncertainties, the nominal derived merger rate is ~5 x 10^-4 per yr in the Milky Way, just ~3-6 and ~20-40 times less than the Type Ia and core-collapse supernova (SN) rates, respectively. This implies that the merger rate is ~0.5-1 x 10^4 per Gpc^3 per yr in the local universe, ~5000-10000 times more than the observed (beaming-uncorrected) long-duration gamma-ray burst (GRB) rate. We estimate the lower limit on the rate in the Galaxy to be >2.5 x 10^-5 per yr at 95% confidence. We briefly discuss the implications of this finding for the census of long- and short-duration GRBs and their progenitors, the frequency of tight binary companions to Type Ib/c SN progenitors, the origin of ultra-high energy cosmic rays (UHECRs), the formation of rapidly rotating neutron stars and ~2-3 M_sun black holes, the census of faint Ia-like SNe, as well as for upcoming and current transient surveys (e.g., LOSS, PTF, LSST), and for high- (LIGO) and low-frequency (LISA) gravitational wave searches.

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Todd A. Thompson, Matthew D. Kistler, K. Z. Stanek. 2009-12-01. A High Rate of White Dwarf-Neutron Star Mergers & Their Transients. https://arxiv.org/abs/0912.0009

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