Inverse comptonization and the nature of the March 1979 γ-ray burst event

Abstract

The central issue concerning the nature of the 5 March 1979 γ-ray burst is that of whether its source is the supernova remnant N49 in the Large Magellanic Cloud (LMC), whose extragalactic distance implies unusually high (super-Eddington) luminosity. Although the optically thin synchrotron mechanism proposed by Ramaty et al.1 has met many of the earlier theoretical objections, other evidence is needed to support or disprove such an extragalactic origin. I point out here that the observed2 burst spectrum seems to be most naturally and consistently interpreted as that of a synchrotron spectrum modified by inverse Compton scattering from ∼Me V e±-pairs. (Inverse Comptonization describes the gain of energy by photons as a result of scattering with electrons of much higher energy.) This model then allows us to derive, from first principles, the intrinsic synchrotron luminosity of the burst source, which agrees basically with that expected from N49 (distance ∼55 kpc).