Volume 431, Number 1, February III 2005
|Page(s)||175 - 182|
|Section||Interstellar and circumstellar matter|
|Published online||02 February 2005|
Mid-IR observations of circumstellar disks*
II. Vega-type stars and a post-main sequence object
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: email@example.com
2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
3 European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile
Accepted: 10 September 2004
We present spectral energy distributions and new N-band photometry and spectroscopy for a sample of six main sequence stars and one post-MS object using the ESO TIMMI2 camera at La Silla observatory (Chile). All objects are thought to possess circumstellar material and for the majority of the targets this is their first N-band spectroscopic observation. The emission spectra (observed in three cases), modelled with a mixture of silicates consisting of different grain sizes and composition, confirm the suspected presence of disks around these targets. The most important discovery is that HD 113766, a young Vega-type star, is host to highly processed dust which is probably second generation. It is the first time a Vega-type star with such highly evolved dust has been observed. Silicate emission of basically unevolved dust is seen in case of the post-MS object HD 41511 and the Vega-type star HD 172555. In addition, to study the cold dust, we observed a subsample at 1200 μm with the bolometer array SIMBA at the SEST in La Silla but we only got upper limits for those five objects. This shows that these Vega-type stars have a smaller amount of dust than their precursors, the T Tauri and Herbig Ae/Be stars.
Key words: stars: circumstellar matter / stars: planetary systems: protoplanetary disks / infrared: stars / techniques: spectroscopic / submillimeter
© ESO, 2005
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