Gamma‐Ray Bursts from High‐Velocity Neutron Stars

Abstract

We investigate the viability of Galactic corona models of gamma-ray bursts by calculating the spatial distribution expected for a population of high-velocity neutron stars born in the Galactic disk and moving in a gravitational potential that includes contributions from the bulge, disk, and dark matter halo of our Galaxy and also from these same components of our neighboring galaxy M31. We consider two classes of models: one in which the bursts radiate isotropically and one in which the bursts are beamed. We place constraints on these models by comparing the expected brightness and angular distributions with the data in the BATSE 3B catalog. We find that if the bursts radiate isotropically, then the Galactic corona model can reproduce the BATSE peak flux and angular distributions for neutron star kick velocities vkick 800 km s-1, source turn-on ages ton 20 Myr, and BATSE sampling distances 130 kpc dmax 350 kpc. If the bursts are instead beamed with an opening half-angle ?b, no turn-on age is required, and the model can reproduce the BATSE data for 15? ?b 20? and 80 kpc dmax 250 kpc.