Astrophysics, abstract
astro-ph/0512654

From: Jonathan E. Grindlay [view email]

Date: Fri, 30 Dec 2005 20:24:37 GMT (37kb)

Short gamma-ray bursts from binary neutron star mergers in globular clusters

Authors: Jonathan Grindlay (1), Simon Portegies Zwart (2), Stephen McMillan (3) ((1) Harvard-Smithsonian Center for Astrophysics, (2) Astronomical Institute Anton Pannekoek, (3) Department of Physics, Drexel University)

Comments: 13 pages, 2 figures, accepted for publication in Nature Physics (Feb. 2006)

The first locations of short gamma-ray bursts (GRBs) in elliptical galaxies suggest they are produced by the mergers of double neutron star (DNS) binaries in old stellar populations. Globular clusters, where the extreme densities of very old stars in cluster cores create and exchange compact binaries efficiently, are a natural environment to produce merging NSs. They also allow some short GRBs to be offset from their host galaxies, as opposed to DNS systems formed from massive binary stars which appear to remain in galactic disks. Starting with a simple scaling from the first DNS observed in a galactic globular, which will produce a short GRB in ~300My, we present numerical simulations which show that ~10-30% of short GRBs may be produced in globular clusters vs. the much more numerous DNS mergers and short GRBs predicted for galactic disks. Reconciling the rates suggests the disk short GRBs are more beamed, perhaps by both the increased merger angular momentum from the DNS spin-orbit alignment (random for the DNS systems in globulars) and a larger magnetic field on the secondary NS.

http://arxiv.org/abs/astro-ph/0512654

Release No.: 06-12

For Release: Tuesday, January 31, 2006

Note to editors: Images to accompany this release are online at

http://www.cfa.harvard.edu/press/pr0612image.html.

Neutron Star Swaps Lead to Short Gamma-Ray Bursts

Cambridge, MA - Gamma-ray bursts are the most powerful explosions in the universe, emitting huge amounts of high-energy radiation. For decades their origin was a mystery. Scientists now believe they understand the processes that produce gamma-ray bursts. However, a new study by Jonathan Grindlay of the Harvard-Smithsonian Center for Astrophysics (CfA) and his colleagues, Simon Portegies Zwart (Astronomical Institute, The Netherlands) and Stephen McMillan (Drexel University), suggests a previously overlooked source for some gamma-ray bursts: stellar encounters within globular clusters.

"As many as one-third of all short gamma-ray bursts that we observe may come from merging neutron stars in globular clusters," said Grindlay.

http://www.cfa.harvard.edu/press/pr0612.html