Unthermalized plasma in bursts sources

Abstract

The pair e(+)-e(-) annihilation phenomena in hot plasma was studied in order to evaluate the photon energy spectrum. The spectra of the broadening 0.511 MeV annihilation line was calculated in the case of unthermalized plasma, i.e., T sub e(-) does not equal T sub e(+). The energy spectra from annihilation process for unthermalized positrons are characterized by the presence of flat part for energies greater than 0.511 MeV. The flattening in the spectrum of annihilation unthermalized plasma is a strong indication that the observed features of the hard tailed spectrum of the gamma bursts can be well described by annihilation of hot positrons and cold electrons. It is proposed that the mechanism for the production of unthermalized positrons is associated with the charge separation in Eddington limited accretion onto a neutron star.