Models of magnetized neutron star atmospheres

TL;DR

This paper introduces a comprehensive computer model for simulating magnetized neutron star atmospheres across a wide range of magnetic fields and temperatures, accounting for various plasma compositions and physical effects.

Contribution

The authors develop a novel code that models neutron star atmospheres with detailed physics, including vacuum resonance and mode conversion, for different magnetic inclinations and plasma compositions.

Findings

Thin hydrogen atmospheres with vacuum polarization can explain observed spectra.

The 'sandwich' atmosphere model reproduces features of RBS 1223.

The code enables detailed spectral analysis of magnetized neutron stars.

Abstract

We present a new computer code for modeling magnetized neutron star atmospheres in a wide range of magnetic fields (10^{12} - 10^{15} G) and effective temperatures (3 \times 10^5 - 10^7 K). The atmosphere is assumed to consist either of fully ionized electron-ion plasmas or of partially ionized hydrogen. Vacuum resonance and partial mode conversion are taken into account. Any inclination of the magnetic field relative to the stellar surface is allowed. We use modern opacities of fully or partially ionized plasmas in strong magnetic fields and solve the coupled radiative transfer equations for the normal electromagnetic modes in the plasma. Using this code, we study the possibilities to explain the soft X-ray spectra of isolated neutron stars by different atmosphere models. In particular, the outgoing spectrum using the "sandwich" model (thin atmosphere with a hydrogen layer above a helium layer) is constructed. Thin partially ionized hydrogen atmospheres with vacuum polarization are shown to be able to improve our understanding of the observed spectrum of the nearby isolated neutron star RBS 1223 (RX J1308.8+2127).