  We present a detailed investigation of atmospheres around accreting neutron
stars with high magnetic field ($B\gtrsim 10^{12}$ G) and low luminosity
($L\lesssim 10^{33}$ erg/s). We compute the atmospheric structure, intensity
and emergent spectrum for a plane-parallel, pure hydrogen medium by solving the
transfer equations for the normal modes coupled to the hydrostatic and energy
balance equations. The hard tail found in previous investigations for
accreting, non-magnetic neutron stars with comparable luminosity is suppressed
and the X-ray spectrum, although still harder than a blackbody at the star
effective temperature, is nearly planckian in shape. Spectra from accreting
atmospheres, both with high and low fields, are found to exhibit a significant
excess at optical wavelengths above the Rayleigh-Jeans tail of the X-ray
continuum.

Astrophysics