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Do Gamma-Ray Bursts Originate from an Extended Galactic Halo of High-Velocity Neutron Stars?

Published online by Cambridge University Press:  12 April 2016

Dieter H. Hartmann
Affiliation:
Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-1911
Lawrence E. Brown
Affiliation:
Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-1911
Lih-Sin The
Affiliation:
Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-1911
Eric V. Linder
Affiliation:
Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305
Vahé Petrosian
Affiliation:
Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305
George R. Blumenthal
Affiliation:
UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064
Kevin C. Hurley
Affiliation:
Space Sciences Laboratory, University of California at Berkeley, Berkeley CA 94720

Abstract

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The γ-ray burst brightness distribution is inhomogeneous and the distribution on the sky is nearly isotropic. These features argue against an association of γ-ray bursts with those Galactic objects that are known to exhibit a strong concentration toward the Galactic center or plane. The observed statistical properties indicate a cosmological origin. Circumstantial evidence suggests that neutron stars are involved in the burst phenomenon. Here we consider Population II neutron stars in an extended Galactic Halo (EGH) as an alternative to cosmological scenarios. The BATSE data indicate a small deviation from isotropy near the 2 σ level of statistical significance. If confirmed for an increasing number of bursts, these anisotropies could rule out cosmological scenarios. On the other hand, EGH models require small anisotropies like those observed by BATSE. We consider simple distribution models to determine the generic properties such halos must have to be consistent with the observations and discuss the implications of the corresponding distance scale on burst models.

Subject headings: gamma rays: bursts — stars: neutron — stars: Population II — stars: statistics

Type
Gamma-Ray Bursts and UHE Sources
Copyright
Copyright © The American Astronomical Society 1994

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