Volume 507, Number 1, November III 2009
|Page(s)||261 - 276|
|Section||Interstellar and circumstellar matter|
|Published online||27 August 2009|
Mid-IR observations of circumstellar disks *
Part III. A mixed sample of PMS stars and Vega-type objects
European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile e-mail: email@example.com
2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
3 NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035, USA
4 SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA
5 The University of Western Ontario, London, ON N6A 3K7, Canada
Accepted: 17 April 2009
We present new mid-infrared spectra of 15 targets (1 FU Orionis object, 4 Herbig Ae stars, 5 T Tauri stars, and 5 Vega-type stars), obtained with the TIMMI2 camera at La Silla Observatory (ESO). Three targets are members of the β Pic moving group (HD 155 555, HD 181 296, and HD 319 139). PAH bands are observed towards the T Tauri star HD 34 700 and the Herbig Ae star PDS 144 N. For HD 34 700, the band profiles indicate processed PAHs. The spectrum of the Vega-type object η Corvi (HD 109 085), for which a resolved disk at sub-mm wavelengths is known, appears stellar between 8–13 μm, but a small excess emission was reported by Spitzer observations. Similarly, no indication of circumstellar matter at mid-infrared wavelengths is found towards the Vega-like stars HD 3003, HD 80 951, HD 181 296, and, surprisingly, the T Tauri system HD 155 555. The silicate emission features of the remaining eight sources are modelled with a mixture of silicates of different grain sizes and composition. Unprocessed dust dominates FU Ori, HD 143 006, and CD-43 344. Large amorphous grains are the main dust component around HD 190 073, HD 319 139, KK Oph, and PDS 144 S. Both small grains and crystalline dust is found for the Vega-type HD 123 356, with a dominance of small amorphous grains. We show that the infrared emission of the binary HD 123 356 is dominated by its late-type secondary, but optical spectroscopy is still required to confirm the age of the system and the spectral class of the companion. For most targets, this is their first mid-infrared spectroscopic observation. We investigate trends between stellar, disk, and silicate properties and confirm correlations identified in previous studies. Several objects present an exciting potential for follow-up high-resolution disk studies.
Key words: methods: observational / techniques: spectroscopic / stars: circumstellar matter / infrared: stars / stars: planetary systems: protoplanetary disks / stars: pre-main sequence
© ESO, 2009
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