Numerical calculation of magnetobremsstrahlung emission and absorption coefficients

Magnetobremsstrahlung (MBS) emission and absorption play a role in many astronomical systems. We describe a general numerical scheme for evaluating MBS emission and absorption coefficients for both polarized and unpolarized light in a plasma with a general distribution function. Along the way we provide an accurate scheme for evaluating Bessel functions of high order. We use our scheme to evaluate the accuracy of earlier fitting formulae and approximations. We also provide an accurate fitting formula for mildly relativistic (kT/(m _ec ²) ≳ 0.5) thermal electron emission (and therefore absorption). Our scheme is too slow, at present, for direct use in radiative transfer calculations but will be useful for anyone seeking to fit emission or absorption coefficients in a particular regime.