2009/11/04 by S. Kraus, Stefan Kraus, K. -H. Hofmann +7
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Be star #Brightness #Circumstellar dust #Cosmic dust #Debris disk #Galaxy #Herbig Ae/Be star #Interferometry #Luminosity #Physics #Planet #Planetary system #Position angle #Spectral energy distribution #Stars #Stellar, planetary, and galactic studies #Surface brightness #T Tauri star #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/200912990
17 pages; 15 figures; Accepted by A&A
openalex publication_date 2009/11/04 · arxiv created 2009/11/18 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
<i>Context. <i/>Unveiling the structure of the disks around intermediate-mass pre-main-sequence stars (Herbig Ae/Be stars) is essential for our understanding of the star and planet formation process. In particular, models predict that in the innermost AU around the star, the dust disk forms a “puffed-up” inner rim, which should result in a strongly asymmetric brightness distribution for disks seen under intermediate inclination.<i>Aims. <i/>Our aim is to constrain the sub-AU geometry of the inner disk around the Herbig Ae star R CrA and search for the predicted asymmetries.<i>Methods. <i/>Using the VLTI/AMBER long-baseline interferometer, we obtained 24 near-infrared (<i>H<i/>- and <i>K<i/>-band) spectro-interferometric observations on R CrA. Observing with three telescopes in a linear array configuration, each data set samples three equally spaced points in the visibility function, providing direct information about the radial intensity profile. In addition, the observations cover a wide position angle range (~97°), also probing the position angle dependence of the source brightness distribution.<i>Results. <i/>In the derived visibility function, we detect the signatures of an extended (Gaussian <i>FWHM<i/> ~ 25 mas) and a compact component (Gaussian <i>FWHM<i/> ~ 5.8 mas), with the compact component contributing about two-thirds of the total flux (both in <i>H<i/>- and <i>K<i/>-band). The brightness distribution is highly asymmetric, as indicated by the strong closure phases (up to ~40°) and the detected position angle dependence of the visibilities and closure phases. To interpret these asymmetries, we employ various geometric as well as physical models, including a binary model, a skewed ring model, and a puffed-up inner rim model with a vertical or curved rim shape. For the binary and vertical rim model, no acceptable fits could be obtained. On the other hand, the skewed ring model and the curved puffed-up inner rim model allow us to simultaneously reproduce the measured visibilities and closure phases. From these models we derive the location of the dust sublimation radius (~0.4 AU), the disk inclination angle (~35°), and a north-south disk orientation (PA ~ 180-190°). Our curved puffed-up rim model can reproduce reasonably well the interferometric observables and the SED and suggests a luminosity of ~29 and the presence of relatively large (1.2 <i>μ<i/>m) Silicate dust grains. Our study also reveals discrepancies between the measured interferometric observables and the puffed-up inner rim models, providing important constraints for future refinements of these theoretical models. Perpendicular to the disk, two bow shock-like structures appear in the associated reflection nebula NGC 6729, suggesting that the detected sub-AU size disk is the driving engine of a large-scale outflow.<i>Conclusions. <i/>Detecting, for the first time, strong non-localized asymmetries in the inner regions of a Herbig Ae disk, our study supports the existence of a puffed-up inner rim in YSO disks.