Improved calculations of electron-ion Bremsstrahlung Gaunt factors for astrophysical applications

Electron-ion Bremsstrahlung (free-free) emission and absorption occur in many astrophysical plasmas for a wide range of physical conditions. This classical problem has been studied multiple times, and many analytical and numerical approximations exist. However, accurate calculations of the transition from the non-relativistic to the relativistic regime remain sparse. Here we provide a comprehensive study of the free-free Gaunt factors for ions with low charge (Z
12 pages + 5 pages appendix and references, 17 figures, to be submitted to MNRAS, BRpack will be made available at www.chluba.de/BRpack