Abstract
THE angular and luminosity distributions of the y–ray bursts observed by the BATSE instrument, on the Gamma Ray Observatory satellite, cannot be explained by sources confined to the galactic plane1. Instead the observations are consistent with a nearly isotropic source density that falls with distance. Although this permits a cosmological origin, it also permits an origin in the halo of our Galaxy, preserving some aspects of models in which galactic neutron stars are the sites of the bursts. I show here that significant isotropy can be achieved with a spherically symmetric halo model if it extends out beyond 100 kpc. Large halo core radii enhance isotropy, although consistency with observation is possible for core radii as small as 5 kpc if the halo radius is sufficiently large. The intrinsic luminosity distribution of y–ray bursts must be treated as a free parameter to fit the observations. If y–ray bursts are from the halo, they are likely to be old population II neutron stars, because models based on pulsars escaping from the galactic plane have strong anisotropies.
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Brainerd, J. Gamma-ray bursts in the galactic halo. Nature 355, 522–524 (1992). https://doi.org/10.1038/355522a0
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DOI: https://doi.org/10.1038/355522a0
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