γ-ray Bursts and the Diffuse Flux of Cosmic X-rays

Abstract

MANY attempts have been made to explain the diffuse cosmic X-ray flux in terms of contributions from a large number of discrete extragalactic sources. The nature of these sources has remained obscure; the steady emission from normal galaxies, such as our own, fails by more than an order of magnitude to explain the intensity of the diffuse flux¹. The spectrum of the diffuse flux can be approximated to a power law (ɛ in keV) for values of ɛ from 1 keV to 1 MeV. This poses a further problem because the spectrum is much harder than that of the discrete extragalactic sources which have been detected. Klebesadel et al.² have recently reported observations of bursts of radiation with hard spectra which extend to photon energies greater than 1 MeV. Here I shall show that, whatever is the nature of the sources of these bursts, they are unlikely to make a significant contribution to the diffuse flux.