Volume 552, April 2013
|Number of page(s)||13|
|Section||Interstellar and circumstellar matter|
|Published online||13 March 2013|
Sculpting the disk around T Chamaeleontis: an interferometric view⋆
1 Max Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2 UJF – Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, France
3 European Southern Observatory, Alonso de Cordova, 3107 Vitacura, Chile
4 LESIA – Observatoire de Paris, CNRS, UPMC Univ. Paris 6, Univ. Paris-Diderot, 92195 Meudon, France
5 UMI – FCA, CNRS / INSU France (UMI 3386) , and Departamento de Astronomía, Universidad de Chile, Santiago, Casilla 36D, Chile
6 Université de Nice – Sophia Antipolis/CNRS/Observatoire de la Côte d’Azur, Laboratoire Lagrange (UMR 7293), Boulevard de l’Observatoire, BP 4229, 06304 Nice Cedex 04, France
7 Max-Planck Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr, 85741 Garching, Germany
8 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, 28049 Madrid, Spain
9 Universitäts Sternwarte München, Ludwig Maximilians Universität, Scheinerstr. 1, 81679 München, Germany
10 Jet Propulsion Laboratory (NASA/JPL), MS 301-355, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA
Received: 31 October 2012
Accepted: 6 February 2013
Context. Circumstellar disks are believed to be the birthplace of planets and are expected to dissipate on a timescale of a few Myr. The processes responsible for the removal of the dust and gas will strongly modify the radial distribution of the circumstellar matter and consequently the spectral energy distribution. In particular, a young planet will open a gap, resulting in an inner disk dominating the near-IR emission and an outer disk emitting mostly in the far-infrared.
Aims. We analyze a full set of data involving new near-infrared data obtained with the 4-telescope combiner (VLTI/PIONIER), new mid-infrared interferometric VLTI/MIDI data, literature photometric and archival data from VLT/NaCo/SAM to constrain the structure of the transition disk around T Cha.
Methods. After a preliminary analysis with a simple geometric model, we used the MCFOST radiative transfer code to simultaneously model the SED and the interferometric observables from raytraced images in the H-, L′-, and N-bands.
Results. We find that the dust responsible for the strong emission in excess in the near-IR must have a narrow temperature distribution with a maximum close to the silicate sublimation temperature. This translates into a narrow inner dusty disk (0.07–0.11 AU), with a significant height (H/r ~ 0.2) to increase the geometric surface illuminated by the central star. We find that the outer disk starts at about 12 AU and is partially resolved by the PIONIER, SAM, and MIDI instruments. We discuss the possibility of a self-shadowed inner disk, which can extend to distances of several AU. Finally, we show that the SAM closure phases, interpreted as the signature of a candidate companion, may actually trace the asymmetry generated by forward scattering by dust grains in the upper layers of the outer disk. These observations help constrain the inclination and position angle of the disk to about + 58° and − 70°, respectively.
Conclusions. The circumstellar environment of T Cha appears to be best described by two disks spatially separated by a large gap. The presence of matter (dust or gas) inside the gap is, however, difficult to assess with present-day observations. Our model suggests the outer disk contaminates the interferometric signature of any potential companion that could be responsible for the gap opening, and such a companion still has to be unambiguously detected. We stress the difficulty to observe point sources in bright massive disks, and the consequent need to account for disk asymmetries (e.g. anisotropic scattering) in model-dependent search for companions.
Key words: stars: individual: T Cha / circumstellar matter / infrared: stars / techniques: interferometric
© ESO, 2013
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