Surface Emission Properties of Strongly Magnetic Neutron Stars

We construct radiative equilibrium models for strongly magnetic (B > 10^13 G) neutron-star atmospheres taking into account magnetic free-free absorption and scattering processes computed for two polarization modes and including the effects of vacuum polarization. We present temperature profiles and the angle-, photon energy-, and polarization-dependent emerging intensity for a range of magnetic field strengths and effective temperatures of the atmospheres. We find that for B < 10^14 G, the emerging spectra are bluer than the blackbody corresponding to the effective temperature, T_eff, with modified Planckian shapes. However, vacuum polarization significantly modifies the spectra for B~10^15 G, giving rise to power-law tails at high photon energies. The angle-dependence (beaming) of the emerging intensity has two maxima: a narrow (pencil) peak at small angles (