The possible galactic origin of γ-ray bursts

Abstract

FOLLOWING the discovery of non-solar γ-ray bursts¹, various models to account for their origin have been discussed. Extragalactic models include supernova bursts in remote galaxies², and the collapse of the cores in active stars³, while galactic models are based on flare stars⁴, thermonuclear explosions on neutron stars⁵ and the sudden accretion of cometary gas on to neutron stars⁶. The acceptability of any of these models may be tested by the observed size spectrum of γ-ray bursts. The extragalactic models predict a power law spectrum with α = −1.5 while for the galactic models the number index will be −1. The experimental data on γ-ray bursts is still meagre. So far, about 44 confirmed events have been recorded by satellite-borne instruments^7,8. The number spectrum of the observed γ-ray bursts (Fig. 1) shows that the observed distribution for events with an energy less than 10⁻⁴ erg cm⁻² is flat and thus makes the choice of any model completely arbitrary. Carter et al.⁹ presented an upper limit on the number of γ-ray bursts having an energy > 2.10⁻⁷ erg cm⁻² and suggested that the data are consistent with a power law spectrum in which α ∼ 0.5, or a modified galactic distribution. We present here an alternative analysis of the observed γ-ray events, which suggests very interesting possibilities for their origin.