## [1202.2179] The Swift short gamma-ray burst rate density: implications for binary neutron star merger rates

Authors: David Coward, Eric Howell, Tsvi Piran, Giulia Stratta, Marica Branchesi, Omer Bromberg, Bruce Gendre, Ronald Burman, Dafne Guetta

Date: 10 Feb 2012

Abstract: Short gamma-ray bursts (SGRBs) observed by {\it Swift} are potentially revealing the first insight into cataclysmic compact object mergers. To ultimately acquire a fundamental understanding of these events requires pan-spectral observations and knowledge of their spatial distribution to differentiate between proposed progenitor populations. Presently (late 2011) there are only some 30% of SGRBs with reasonably firm redshifts, and this sample is highly biased by the limited sensitivity of {\it Swift} to detect SGRBs. We account for the dominant biases to calculate a realistic SGRB rate density out to $z\approx0.5$ using the {\it Swift} sample of peak fluxes, redshifts, and those SGRBs with a beaming angle constraint from X-ray/optical observations. We find an SGRB lower rate density of $7.1ˆ{+4.9}_{-3.2}$ $\mathrm{Gpc}ˆ{-3}\mathrm{yr}ˆ{-1}$ (assuming isotropic emission), and a beaming corrected upper limit of $1200ˆ{+840}_{-550}$ $\mathrm{Gpc}ˆ{-3}\mathrm{yr}ˆ{-1}$. Assuming a significant fraction of binary neutron star mergers produce SGRBs, we calculate lower and upper detection rate limits of $(1-200)$ yr$ˆ{-1}$ by an ALIGO and Virgo coincidence search. Our detection rate is similar to the lower and realistic rates inferred from extrapolations using Galactic pulsar observations and population synthesis.

#### Feb 12, 2012

1202.2179 (/preprints)
2012-02-12, 23:17