Since several gamma-ray bursts seem to have their origin in the vicinity of neutron stars, where strong magnetic fields are present (B ≃ 108T), electrons and positrons have to be described, in this instance, by relativistic Landau states. As is well known, strong magnetic fields produce important effects: motion perpendicular to the field is quantized, transverse momentum is not conserved, and polarization effects become important. Moreover, in contrast to the field-free case, exotic processes such as 1γ pair-annihilation are not forbidden. With growing magnetic field, the cross section of this process becomes more and more nonnegligible. This cross section strongly depends on the polarization of the electron-positron pairs. Thus the deceleration via annihilation turns out to be a strongly polarization-dependent phenomenon in magnetized electron-positron plasmas.

Subject headings: acceleration of particles — gamma rays: theory — polarization — radiation mechanisms: nonthermal — stars: neutron