Short gamma-ray bursts (SGRBs) observed by Swift potentially reveal 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. Up to 2012 April, there are only some 30 per cent of SGRBs with reasonably firm redshifts, and this sample is highly biased by the limited sensitivity of Swift to detect SGRBs. We account for the dominant biases to calculate a realistic SGRB rate density out to z ≈ 0.5 using the 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 8-3+5 Gpc -3 yr -1 (assuming isotropic emission) and a beaming corrected upper limit of 1100-470+700 Gpc -3 yr -1. Assuming a significant fraction of binary neutron star mergers produce SGRBs, we calculate lower and upper detection rate limits of (1-180) yr-1 by an Advanced LIGO (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

The Laser Interferometer Gravitational-Wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new Bayesian 90% upper limit is GW ; H 0 / 72 km s À1 Mpc À1 À Á Â Ã 2 < 6:5 ; 10 À5 . This is currently the most sensitive result in the frequency range 51Y150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss the complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.

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We show that if the observed surface density function of supernovae in external spiral galaxies is used to calibrate the historical data on the supernova rate in the solar neighbourhood, then the calculated total supernova rate for the Galaxy is abnormally high. This can be explained if Galactic supernovae are not uniformly distributed over the Galactic disc, but tend to be localized near spiral arms and star‐forming regions. Such a distribution would be consistent with evidence for an association of Type Ib/c and Type II supernovae with H ii regions in late‐type galaxies. It seems that we occupy a privileged position in the Milky Way ‐‐ one which gives us the impression of a considerably higher supernova rate than is valid for the Galaxy as a whole.

We report results from a search for gravitational waves produced by perturbed intermediate mass black holes (IMBH) in data collected by LIGO and Virgo between 2005 and 2010. The search was sensitive to astrophysical sources that produced damped sinusoid gravitational wave signals, also known as ringdowns, with frequency 50 ≤ f 0 =Hz ≤ 2000 and decay timescale 0.0001 ≲ τ=s ≲ 0.1 characteristic of those produced in mergers of IMBH pairs. No significant gravitational wave candidate was detected. We report upper limits on the astrophysical coalescence rates of IMBHs with total binary mass 50 ≤ M=M ⊙ ≤ 450 and component mass ratios of either 1:1 or 4:1. For systems with total mass 100 ≤ M=M ⊙ ≤ 150, we report a 90% confidence upper limit on the rate of binary IMBH mergers with nonspinning and equal mass components of 6.9 × 10 −8 Mpc −3 yr −1 . We also report a rate upper limit for ringdown waveforms from perturbed IMBHs, radiating 1% of their mass as gravitational waves in the fundamental, l ¼ m ¼ 2, oscillation mode, that is nearly three orders of magnitude more stringent than previous results.