The Radio and Infrared Spectrum of Early-type Stars Undergoing Mass Loss

Abstract

A unified model is presented for the radio and IR spectrum of early-type stars surrounded by a gaseous ionized envelope resulting from mass loss. The cases of uniform mass loss (i) at constant velocity, and (ii) with accelerative effects taken into account, are treated. It is shown that the radio and infrared free-free spectra are predicted to be of the form S~freq^0.6 except (typically) in the NIR where the spectrum will become flatter. Various effects which may cause a deviation from the 0.6 spectral index are considered. Finally, it is shown how radio and IR flux densities may be used to dervie mass loss rates and obtain lower limits to the number of ionizing photos emitted per second by the underlying stars.