On the extended halo origin of gamma-ray bursts

Abstract

The γ‐ray burst brightness distribution is inhomogeneous and their distribution on the sky is nearly isotropic. These features argue against an association of γ‐ray bursts with Galactic objects whose spatial distribution is similar to that a Population I tracers. Circumstantial evidence suggests that neutron stars are involved in the burst phenomenon. We consider Population II neutron stars in an extended Galactic halo (EGH) as an alternative to cosmological scenarios. The BATSE data presented at this conference suggest deviations from isotropy slightly below the 2 σ level of statistical significance. If confirmed by additional data, the anisotropies would rule out cosmological scenarios. Extended halo models predict small anisotropies like those observed by BATSE. We consider simple EGH models to determine the generic properties such halos must have to be consistent with the observational constraints.