Radiative Opacities and Photosphere Models for Soft Gamma-Ray Repeaters

INTRODUCTION The presence of superstrong magnetic fields, B ¸ 10 14 \Gamma 10 16 G, in radiating layers of SGRs has been suggested in (1) to explain the apparent superEddington luminosities observed from these enigmatic sources of thermal-like radiation with spectral temperatures T sp ¸ 10 keV. This hypothesis is based on strong suppression of the electron Thomson scattering cross section for radiation polarized perpendicular to the magnetic field at photon energies lower than the electron cyclotron energy E Be = 11:6B 15 MeV. According to (1--5), this effect can substantially reduce the radiative force and increase the critical luminosity above the observed SGR luminosities, L ¸ 10 42 erg/s. If the SGR magnetic fields are indeed so strong, the opacity can be significantly contribute