### Abstract

The intensity and polarization of two-photon annihilation in a magnetic fuield B≪B_{cr}=4.4×10^{13} G are studied in detail for a, one-dimensional thermal distribution of annihilating electrons and positrons on the ground Landau level. With the increase of temperature T the total annihilation rate and energy losses decrease, being higher than for the isotropic thermal distributions at the same T. The shapes of intensity spectra at sin ρ{variant}=0 (ρ{variant} is the angle between B and wave-vector) are close to those in the isotropic case. The widths and blue-shifts of the spectra decrease with increasing sin ρ{variant} and increase with increasing T. Logarthmic singularities arise in the spectra at E»mc^{2}/sin ρ{variant}. Power-like parts are formed in the wings of the spectra for kT≫mc^{2} and not too small sin ρ{variant}. The direction-integrated spectra reach their (finite) maxima, at E=mc^{2} for any T. The radiation concentrates near the plane, perpendicular to the magnetic field for E close to mc^{2} and is beamed along the magnetic field for E far from mc^{2}. Energy-integrated angular distributions are stretched along B, the stronger the higher T. The rediation is linearly polarized in the plane formed by the magnetic field and weve-vector. Typical values of the polarization inside the cores of the annihilation spectra are ∼(kT/mc^{2}) sin ρ{variant} and [ln (kT/mc^{2})]^{-1} for kT≪mc^{2} and kT sin ρ{variant}≫mc^{2}, respectively. Annihilation radiation dominates over Bremsstrahlung in the e^{∓} plasma at kT≲7 mc^{2}. The results are useful for interpretation of the annihilation radiation in the gamma-ray bursts. They permit to estimate temperature, gravitational potential, and emission measure of radiating regions and the beaming of the radiation.

Original language | English (US) |
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Pages (from-to) | 241-284 |

Number of pages | 44 |

Journal | Astrophysics and Space Science |

Volume | 174 |

Issue number | 2 |

DOIs | |

State | Published - Dec 1 1990 |

### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

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## Cite this

*Astrophysics and Space Science*,

*174*(2), 241-284. https://doi.org/10.1007/BF00642511