A study of dust properties in the inner sub-au region of the Herbig Ae star HD 169142 with VLTI/PIONIER

Chen, Lei and Kóspál, Ágnes and Ábrahám, Péter and Kreplin, A. and Matter, A. (2018) A study of dust properties in the inner sub-au region of the Herbig Ae star HD 169142 with VLTI/PIONIER. ASTRONOMY & ASTROPHYSICS, 609. ISSN 0004-6361

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Abstract

Context. An essential step to understanding protoplanetary evolution is the study of disks that contain gaps or inner holes. The pre-transitional disk around the Herbig star HD 169142 exhibits multi-gap disk structure, differentiated gas and dust distribution, planet candidates, and near-infrared fading in the past decades, which make it a valuable target for a case study of disk evolution. Aims: Using near-infrared interferometric observations with VLTI/PIONIER, we aim to study the dust properties in the inner sub-au region of the disk in the years 2011-2013, when the object is already in its near-infrared faint state. Methods: We first performed simple geometric modeling to characterize the size and shape of the NIR-emitting region. We then performed Monte-Carlo radiative transfer simulations on grids of models and compared the model predictions with the interferometric and photometric observations. Results: We find that the observations are consistent with optically thin gray dust lying at R_in 0.07 au, passively heated to T 1500 K. Models with sub-micron optically thin dust are excluded because such dust will be heated to much higher temperatures at similar distance. The observations can also be reproduced with a model consisting of optically thick dust at R_in 0.06 au, but this model is plausible only if refractory dust species enduring 2400 K exist in the inner disk. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 190.C-963 and 087.C-0709.

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