Astronomy and Astrophysics Letters dedicated to ISO

SWS observations of young main-sequence stars with dusty circumstellar disks

C. Waelkens L.B.F.M. Waters M.S. de Graauw E. Huygen K. Malfait H. Plets B. Vandenbussche D.A. Beintema D.R. Boxhoorn H.J. Habing A.M. Heras D.J.M. Kester F. Lahuis P.W. Morris P.R. Roelfsema A. Salama R. Siebenmorgen N.R. Trams N.R. van der Bliek E.A. Valentijn P.R. Wesselius


We present SWS full-scan observations of three objects that are thought to be in a stage of evolution between the youngest, embedded, Herbig Ae/Be stars and Beta Pictoris, a young main-sequence star with a circumstellar disk. The 8-12 microns spectra of all three stars cannot be understood in terms of purely amorphous silicates, but require the presence of crystalline silicates in different amounts. Around two objects both oxygen-rich and carbon-rich dust particles are present: the spectrum of HD 100546 displays the full set of UIR features; in the spectrum of HD 142527 both the 3.29 and 3.42 micron emission features are observed, as well as a strong 3.51 micron feature. The spectrum of HD 100546 is extremely rich in silicate features in the spectral range from 20 to 45 microns; some of these features strongly suggest the presence of appreciable amounts of crystalline silicates.

Circumstellar matter - Stars: Individual: HD100546 - Stars: Individual: HD142527 - Stars: Individual: 51 Oph - ISM: abundances - Infrared: ISM: lines and bands

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