RADIO-EMISSION FROM STARS - A SURVEY AT 250-GHZ

We have used the IRAM 30 m-telescope together with the MPIfR bolometer to survey nearly 270 stars of different types for 250 GHz continuum e mission. We compare these data with their low frequency (cm-range) pro perties. Early type stars show very often a deviation from the uniform ly expanding wind model which we tentatively attribute to temperature and/or density fluctuations in their deeper atmospheric layers. For WR stars this deviation seems to depend on the effective temperature. Pr e-main sequence stars usually seem to be surrounded by a shell of warm dust making a substantial contribution to the 250 GHz flux density va lue. We have found especially for nearby giants and supergiants that a layer at the transition from photosphere to chromosphere emits ample 250 GHz radiation. We show that the present data can still be explaine d by a simple uniformly illuminated disk model with the known stellar radius. Optically variable stars are not very strong emitters at 250 G Hz. We preferentially detected the more exotic ones, a few B Lyr-type and symbiotic stars. Comments on many individual objects are given in the appropriate sections.