A new interpretation of emission-like features in γ-ray burst spectra

Abstract

The spectra of γ-ray bursts, which are generally thought to result from a transient phenomenon on a neutron star, extend from the optical up to γ-ray energies. It has recently been suggested1 that the whole spectrum may be due to irradiation of a reprocessing and reflecting boundary near a source of power-law γ-rays with a low-energy cutoff E0 ≈ 300–500 keV. In this picture, the emission at intermediate energy (10 keV≲E≲300–500 keV) results from the reflection of incipient high-energy γ-rays by the surface layers of the underlying neutron star and/or its accretion disk. Some bursts display high-energy (∼400-keV) features, which may be gravitationally redshifted photons produced from the annihilation of electron–positron pairs. This explanation, however, has been open to criticism. I show that an alternative explanation for the high-energy features may be the superposition of the incipient and reflected spectral components near E0.