Benisty, M. and Natta, A. and Isella, A. and Berger, J.-P. and Massi, F. and Le-Bouquin, J.-B and Mérand, A. and Duvert, G. and Kraus, S. and Malbet, F. and Olofsson, J. and Robbe-Dubois, S. and Testi, L. and Vannier, M. and Weigelt, G. (2010) Strong near-infrared emission in the sub-AU disk of the Herbig Ae star HD 163296: evidence of refractory dust? Astronomy and Astrophysics, 511 . Art. No. 74. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20100416-141819655
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We present new long-baseline spectro-interferometric observations of the Herbig Ae star HD 163296 (MWC 275) obtained in the H and K bands with the AMBER instrument at the VLTI. The observations cover a range of spatial resolutions between ~3 and ~12 milliarcseconds, with a spectral resolution of ~30. With a total of 1481 visibilities and 432 closure phases, they represent the most comprehensive (u,v) coverage achieved so far for a young star. The circumstellar material is resolved at the sub-AU spatial scale and closure phase measurements indicate a small but significant deviation from point-symmetry. We discuss the results assuming that the near-infrared excess in HD 163296 is dominated by the emission of a circumstellar disk. A successful fit to the spectral energy distribution, near-infrared visibilities and closure phases is found with a model in which a dominant contribution to the H and K band emission originates in an optically thin, smooth and point-symmetric region extending from about 0.1 to 0.45 AU. At a distance of 0.45 AU from the star, silicates condense, the disk becomes optically thick and develops a puffed-up rim, whose skewed emission can account for the non-zero closure phases. We discuss the source of the inner disk emission and tentatively exclude dense molecular gas as well as optically thin atomic or ionized gas as its possible origin. We propose instead that the smooth inner emission is produced by very refractory grains in a partially cleared region, extending to at least ~ 0.5 AU. If so, we may be observing the disk of HD 163296 just before it reaches the transition disk phase. However, we note that the nature of the refractory grains or, in fact, even the possibility of any grain surviving at the very high temperatures we require ( ~ 2100-2300 K at 0.1 AU from the star) is unclear and should be investigated further.
|Additional Information:||© ESO 2010. Received 15 July 2009. Accepted 3 November 2009. We acknowledge fundings from CNRS and INAF (grant ASI-INAF I/016/07/0). This work was in part performed under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology. We thank A. Sargent and T. Ray for hosting part of this research, and the VLTI team at Paranal for the help in obtaining these data. We thank J.D. Monnier who provided with the IOTA data, and M. Sitko for discussions about the photometric measurements. We are greatful to A. Crida, M. Desort and S. Renard for fruitful discussions. We acknowledge the anonymous referee for his comments that improved the clarity of the paper.|
|Subject Keywords:||protoplanetary disks methods: observational techniques: interferometric stars: pre-main sequence|
|Official Citation:||Strong near-infrared emission in the sub-AU disk of the Herbig Ae star HD 163296: evidence of refractory dust? M. Benisty, A. Natta, A. Isella, J-P. Berger, F. Massi, J-B. Le Bouquin, A. Mérand, G. Duvert, S. Kraus, F. Malbet, J. Olofsson, S. Robbe-Dubois, L. Testi, M. Vannier and G. Weigelt A&A 511 A74 (2010) DOI: 10.1051/0004-6361/200912898|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||16 Apr 2010 23:26|
|Last Modified:||26 Dec 2012 11:58|
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