A test of the galactic origin of gamma-ray bursts

Abstract

Statistical properties of the distribution of gamma-ray bursts (GRBs) are analyzed assuming that bursters are located in the Galactic disk or in the Galactic halo. It is shown that, in almost all models, angular anisotropy as measured with either dipole or quadrupole moments is much stronger and should be much easier to detect than the radial nonuniformity of the source distribution as measured with V/Vmax test. Recent reports that V/Vmax is about 0.4 demonstrate that the 'edge' of GRBs distribution has been reached. Therefore, if the bursters are in the Galaxy, then their distribution in the sky should be very anisotropic, with a large dipole or quadrupole moment for halo or disk origin, respectively. Absence of strong anisotropy would indicate cosmological origin. Another possibility could be a very extended halo origin, with the core radius Rc greater than 17 kpc, the range of observations Dmax greater than 50 kpc, and a spherical density distribution, the set of conditions that would be very difficult to understand.