Mid-IR observations of circumstellar disks

Abstract

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.

Polarimetry of the binary PDS 144

“…On the other hand, PDS 144S, with a low polarization, can be reproduced by later YSOs with small grains (SL and SH models) or a combination of earlier (LA) or later YSOs (SH) with large grains. Interestingly, these results are consistent with the mid-IR spectroscopy at N-band of the PDS 144 system by Schütz et al (2009). The PDS 144N spectrum has prominent PAH bands (suggesting very small grains) in a flared disk without any silicate emission.…”

“…Interestingly, PDS 144N is cited as the only Herbig Ae star with an optically thick edge-on disk spatially resolved (Perrin et al 2006, hereafter P06). The two stars are assumed to be the components of a physical binary because they both are pre-main sequence objects, but their circumstellar material is different in composition (Schütz et al 2009) and probably in geometry (P06). The distance of the PDS 144 system is uncertain, but considering the more accepted value (1 kpc), its separation of ∼5400 AU would indicate a really wide binary.…”

A near-infrared interferometric survey of debris-disc stars

“…The excess associated with such a bright exozodiacal disc at a wavelength of 10 µm would amount to almost 20% of the photospheric flux, which would be readily detected by midinfrared spectro-photometry (see e.g. Schütz et al 2009;Lawler et al 2009;Morales et al 2009 spectro-photometry is not available for all our sources, the general absence of large excess at 10 µm suggests that the discs detected by FLUOR are significantly different from the solar zodiacal disc, with much higher dust temperatures. This conclusion has already been made by various authors based on a more thorough modelling of exozodiacal discs using multi-colour interferometric observations (Absil et al 2006;Akeson et al 2009;Defrère et al 2011Defrère et al , 2012Mennesson et al 2013;Lebreton et al 2013).…”

Polycyclic Aromatic Hydrocarbons in Protoplanetary Disks around Herbig Ae/Be and T Tauri Stars

“…Table 1 presents a summary of the data set compiled in this work. (2010), F06: Spitzer/IRS data from Furlan et al (2006), G06: Spitzer/IRS data from Geers et al (2006), G07: VLT/ISAAC data from Geers et al (2007aGeers et al ( , 2007b, K06: Spitzer/IRS data from Kessler-Silacci et al (2006), K08: Spitzer/IRS data from Keller et al (2008), K12: Spitzer/IRS data from Kóspál et al (2012), M10: Spitzer/IRS data from Merín et al (2010), M13: Spitzer/IRS data from Maaskant et al (2013), PHT: ISO/ISOPHOT-S data from Kóspál et al (2012), SpX: IRTF/SpeX data from Smith et al (2004), SWS: Fully processed ISO/SWS atlas (http://isc.astro.cornell.edu/∼sloan/library/swsatlas/atlas.html, Sloan et al 2003), TMM: ESO/TIMMI2 data from Schütz et al (2009), and VSR: VLT/VISIR data from Geers et al (2007b).…”