The effects of winds and coronae of hot stars on the infrared and radio continua.

Abstract

The theory of the formation of infrared and radio continua is extended to include the effects of steep temperature gradients and coronae. The presence of high-temperature zones in the winds from hot stars has been suggested by recent Copernicus satellite observations. We consider models in which the temperature is large only over a small range in radius. The density in the winds of hot stars is high enough for recombination to cool the flow where mechanical energy deposition ceases. Excess radiation at long wavelengths arises in the winds because of the A2 dependence of free-free opacity. We find the coronal region causes a broad bump in the infrared continuum at about 20100 m with a maximum excess of almost 2 mag. Variations of the distribution of density with height can also cause turnover in the continuous energy distribution; however, only temperature decreases, as occurs in the recombination region, can cause spectral gradients much steeper than the Rayleigh-Jeans gradient. Subject headings: stars: coronae - stars: early-type - stars: winds