Surface Emission Properties of Strongly Magnetic Neutron Stars
Abstract
We construct radiative equilibrium models for strongly magnetized (B > 1013 G) neutron-star atmospheres taking into account magnetic free-free absorption and scattering processes computed for two polarization modes. We include the effects of vacuum polarization in our calculations. 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 < 1014 G, the emerging spectra are bluer than the blackbody corresponding to the effective temperature, Teff, with modified Planckian shapes due to the photon-energy dependence of the magnetic opacities. However, vacuum polarization significantly modifies the spectra for B~1015 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 (<5 degrees) with respect to the normal and a broad maximum (fan beam) at intermediate angles (~20-60 degrees). The relative importance and the opening angle of the radial beam decreases strongly with increasing magnetic field strength and decreasing photon energy. We finally compute a Teff-Tc relation for our models, where Tc is the local color temperature of the spectrum emerging from the neutron star surface, and find that Tc/Teff ranges between 1.1-1.8. We discuss the implications of our results for various thermally emitting neutron star models.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.