Volume 500, Number 3, June IV 2009
|Page(s)||1065 - 1076|
|Section||Interstellar and circumstellar matter|
|Published online||29 April 2009|
The flared inner disk of the Herbig Ae star AB Aurigae revealed by VLTI/MIDI in the N-band*
Observatoire de Genève, Université de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland
2 LESIA, Observatoire de Paris, CNRS-UMR-8109, UPMC, Université Paris Diderot, 5 place J. Janssen, 92195 Meudon, France e-mail: firstname.lastname@example.org
3 Université Bordeaux 1; Laboratoire d'Astrophysique de Bordeaux (LAB), France
4 CNRS/INSU – UMR 5804; BP 89, 33270 Floirac, France e-mail: email@example.com
5 UMR 6525 H. Fizeau, Univ. Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, Av. Copernic, 06130 Grasse, France
6 Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
7 University of Kiel, Institute of Theoretical Physics and Astrophysics, Leibnizstrasse 15, 24098 Kiel, Germany
8 Univ. Nice Sophia Antipolis & Obs. de la Côte d'Azur, Laboratoire H. Fizeau, UMR 6525, BP 4229, 06034 Nice Cedex 4, France
Accepted: 2 February 2009
Aims. We aim at using the long baselines of the VLT Interferometer and the mid-IR combiner MIDI (8–13 μm) to derive the morphology of the protoplanetary disk surrounding the Herbig Ae star AB Aurigae
Methods. We present the first N-band analysis of AB Aur performed with a maximum angular resolution of 17 mas (2.5 AU at the Taurus-Auriga distance). We used the radiative transfer code MC3D and a silicate-dominated dust grain mixture to fit the spectral energy distribution (SED), together with the N-band dispersed visibilities ( ~ 30) and to constrain the inner-disk spatial structure.
Results. The silicate band is prominent in the ~ 300 mas FOV of the MIDI instrument, the emission reaches 70 to 90% of the total flux measured by ISO. The circumstellar emission (CSE) is resolved even at the shortest baselines. The spectrally dispersed visibilities show a steep drop between 8 and 9.5 μm, followed by a plateau between 10 and 13 μm. Our modelling shows that the observed SED and visibilities can be reproduced with a simple passive disk model. For such a weakly inclined disk (i ~ 30 deg), the mid-IR visibilities can directly determine the flaring index, while the scale height can be subsequently and unambiguously derived from the combination of the spectral and interferometric constraints. The modelling yields typical values for the scale height of about 8 AU at a radial distance of 100 AU and a flaring index in the range 1.25–1.30 for the explored range of model input parameters.
Conclusions. The radial structure of the circumstellar inner disk around AB Aur is directly determined by MIDI. The radiative transfer modelling demonstrates the powerful synergy of interferometry and spectro-photometry to alleviate the degeneracy, which may hamper determining the disk morphology. Our analysis supports the classification of AB Aur among the flared disks of the first group in the Meeus classification.
Key words: stars: individual: AB Aur / stars: circumstellar matter / stars: pre-main sequence / methods: observational / techniques: interferometric
© ESO, 2009
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