Magnetized Iron Atmospheres for Neutron Stars

Using a Hartree-Fock formalism, we estimate energy levels and photon crosssections for atomic iron in magnetic fields B ~ 10^13 G. Computing ionizationequilibrium and normal mode opacities with these data, we construct LTE neutronstar model atmospheres at 5.5 < Log(T_eff) < 6.5 and compute emergent spectra.We examine the dependence of the emergent spectra on T_eff and B. We also showthe spectral variation with the angle between the magnetic field and theatmosphere normal and describe the significant limb darkening in the X-rayband. These results are compared with recent detailed computations of neutronstar H model atmospheres in high fields and with low field Fe and H modelatmospheres constructed from detailed opacities. The large spectral differencesfor different surface compositions may be discernible with present X-ray data;we also note improvements needed to allow comparison of Fe models with highquality spectra.Comment: 18 pages with 5 eps figures, accepted for publication in ApJ Replaced due to clerical error only: one more author, no new conten