Radio observations of early-type emission-line stars and related objects.

A description is presented of radio observations of 325 objects. Most of the objects are optically unresolved, but a small number have appreciable angular extent. It can be shown that even if the objects are optically unresolved the thermally-emitting gas must be orders of magnitude larger than the associated stars, and they could be referred to as small nebulae. However, that terminology would tend to disguise the intimate connection between the radio-emitting gas and the star, which in all likelihood expelled the gas from its atmosphere some time in the recent past. It is, therefore, preferred to refer to the nebulae as circumstellar shells. The continuum radio spectrum has been determined for several of the thermally-emitting radio stars, and in most cases the spectrum is found to be flat. This is usually interpreted as bremsstrahlung radiation from optically-thin gas.