In section 6. Interstellar and circumstellar matter
Structure of Herbig AeBe disks at the milliarcsecond scale. A statistical survey in the H band using PIONIER-VLTI
The near-infrared excess of intermediate-mass pre-main sequence stars (Herbig AeBe stars) originates in the dust of a circumstellar disk. In this paper, the authors infer the radial and vertical structure of these disks at scales of the order of 1 au. The 51 program objects were observed in the H band (1.6 µm) with the PIONIER/VLTI interferometer and dedicated UBVRIJHK photometric measurements were also obtained. Spectral and geometrical parameters were extracted by fits of a few simple geometrical disk gmodels as well as fits of physical disk models. Sample statistics were evaluated against similar statistics for the physical disk models to derive properties of the sample objects as a group. The authors find that dust at the inner rim of the disk has a sublimation temperature of approx. 1800 K. A ring morphology is confirmed for approximately half the resolved objects; these rings are wide (delta r/r approx. 0.5). A wide ring favors a rim that, on the star-facing side, looks more like a knife edge than a doughnut. The data are also compatible with the combination of a narrow ring and an inner disk of unspecified nature inside the dust sublimation radius. The authors also find, in a significant fraction of the sample, a spatial component that is fully resolved at an angular scale larger than 40 mas. They also find that the presence and relative flux of that component are a property of the Herbig Ae/Be group. Diffusion of starlight off a flared disk is a possible cause of such extended components.