VERY COLD DUST AROUND HERBIG AE/BE STARS

the first results of the isophot gt programme cleinert/herbigae show that the spectral energy distribution of young premain sequence herbig ae/be stars peaks between 100um and 200um. the bulk of the farinfrared emission comes from a compact region around the star, but a comparison with the instrumental beam profile suggests the existence of an extended emission component at 200um as well. the detection of a very cold dust population around herbig stars may be an important contribution by iso to the study of the premain sequence evolution of intermediate mass stars. a more detailed investigation of this dust population is the topic of the present proposal. we propose to observe six herbig ae/be stars from the cleinert/herbigae programme at 150 um using the isophot c200 camera. the goal of these observations is (i) to obtain very precise photomety around the peak of the spectral energy distribution; and (ii) to measure the size of the cold extended component. the data, together with the photometry from cleinert/herbigae, will be used to model the distribution of the cold circumstellar material. the modelling, however, requires information on the extended emission in the 50um100um domain as well. four out of the six stars were observed at 50um and 100um by kao, and two out of these four stars were mapped by isophot. in order to obtain spatial information on the other two stars not observed by kao (v376 cas and lkha 233), we propose to observe them at 60um as well. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]