Some Comments on the Origin of Gamma Ray Bursts

Nakamura Takashi, Shibazaki Noriaki, Murakami Toshio, Yoshida Atsumasa

doi:10.24532/soken.85.3_c110

Recent observation of GRBs (Gamma Ray Burst) by GRO (Gamma Ray Observatory) raised puzzling questions on what GRBs are. At first look of the observational results, the galactic disk origin may be denied due to apparent isotropy and inhomogeneity of the distribution of the source. However, if one takes the lower bound for the quadrupole moment of the distribution of the sources, sources can still be anisotropic. That is, for example, a homogeneous spheroidal distribution of the sources with eccentricity of 0.7 can be compatible with the quadrupole moment and V/V_<max> test within statistical error on 2 to 3σ level. In view of this situation, three possible origins of the gamma ray bursters are discussed in this paper. They are; 1) Comets in Oort like clouds around old neutron stars in the galactic disk falling inside the tidal radius due to perturbation by passing molecular clouds of mass 〜 10^4M_&xodot; and the size 〜 1Opc. 2) Comets around old neutron stars in the galactic halo of size 〜 50kpc which were ejected from globular clusters in their early phase of evolutions and/or were formed in the evolution of Population III stars. 3) Coalescing binary neutron stars at a cosmological distance. We discuss the distribution, the event rate and the energetics for each model.

Some Comments on the Origin of Gamma Ray Bursts

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