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

Abstract

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 8-12μm 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 3.42μm emission features are observed, as well as a strong 3.51μm feature. The spectrum of HD 100546 is extremely rich in silicate features in the spectral range from 20 to 45μm; some of these features strongly suggest the presence of appreciable amounts of crystalline silicates.