Thomas Preibisch, Thomas Driebe, Stefan Kraus, Regis Lachaume, Roy van Boekel, Gerd Weigelt

VLTI MIDI observations of the Herbig Ae star HR 5999

(Contributed Talk)

ESO Workshop: "The power of optical/IR interferometry: recent scientific results and 2nd generation VLTI instrumentation", April 4-8, 2005 in Garching, Germany; F. Paresce, A. Richichi, A. Chelli & F. Delplancke (eds.), Springer-Verlag series ESO Astrophysics Symposia''

Abstract.
We have used long-baseline mid-infrared interferometric observations with MIDI at the VLTI to resolve the circumstellar material around the Herbig Ae star HR~5999 and to provide the first direct measurement of its angular size. The obtained visibilities range between $\sim 0.5$ and $\sim 0.9$ at $10\mu$m. This implies that the mid-infrared emission from HR~5999 is clearly resolved, but has a compact structure not much larger than the resolution limit of the MIDI observations. The characteristic size of the emission region depends on the position angles, and ranges between 10 and 25 milli-arcseconds (corresponding to $\sim 2-5$ AU) for a uniform-disk model, and $5-15$~mas ($\sim 1-3$ AU) for a Gauss model (FWHM). We find a dependence of the characteristic size on the projected baseline position angle, which suggests asymmetry of the emission region. To derive constraints on the geometry of the dust distribution, we compare our interferometric measurements to 2D, frequency-dependent radiation transfer simulations of circumstellar disks.