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.