Abstract

The cyclotron and the one-photon annihilation emissions are investigated for a strongly magnetized thermal electron-positron plasmas. The annihilation spectral component is significant when the particle number density N exceeds some critical value, Ncr(T, B). For T ∼ 108 – 109 K and B ∼ 1012 – 1013 G, this condition can be fulfilled at N < 1022 cm−3, which is realistic for neutron star magnetospheres.

Introduction

The e−e+-plasma in strong magnetic fields of neutron stars can be thought to be responsible for X-ray and γ-ray radiation of radio pulsars and γ-ray bursters. In the emitting regions of these objects, the cyclotron emission and one-photon pair annihilation can be important. Separately, they have been investigated by many authors (see, e.g., Bezchastnov and Pavlov 1991, Harding 1986, 1991, and the references therein). However the comparison of these mechanisms has not been performed even for the simplest case of thermal plasmas. We consider the total emission spectra and find the domain of temperatures T and magnetic fields B where the annihilation component is significant for realistic particle number densities N < 1022 cm−3.

Spectra of radiation

Quantum cyclotron emission and one-photon pair annihilation are characterized by the emissivities (summed over polarizations) jc and ja, respectively.