Thomas Preibisch, Stefan Kraus, Thomas Driebe,
Roy van Boekel, & Gerd Weigelt
A compact dusty disk around the Herbig Ae star HR 5999
resolved with VLTI / MIDI
A&A, 458, 235-243 (2006)
We have used mid-infrared long-baseline interferometry
to resolve the circumstellar material around the Herbig Ae star HR 5999,
providing the first direct measurement of its angular size, and to
derive constraints on the spatial distribution of the dust.
MIDI at the VLTI was used to obtain a set of ten spectrally dispersed
(8-13 micron) interferometric measurements of HR 5999 at different
projected baseline lengths and position angles.
To derive constraints on the geometrical distribution of the dust, we
compared our interferometric measurements to
2D, frequency-dependent radiation transfer simulations of circumstellar
disks and envelopes.
The derived visibility values between ~0.5 and ~0.9 show
that the mid-infrared emission from HR 5999 is clearly resolved.
The characteristic size of the emission region depends on the
projected baseline length and position angle, and it ranges between
~ 5-15 milliarcseconds (Gauss FWHM), corresponding to remarkably
small physical sizes of ~ 1-3 AU.
For disk models with radial power-law density
distributions, the relatively weak but very extended emission from
outer disk regions (>~ 3 AU) leads to
model visibilities that are significantly lower than the
observed visibilities, making these models inconsistent with the MIDI data.
Disk models in which the density is truncated at outer radii of
~ 2-3 AU, on the other hand,
provide good agreement with the data.
A satisfactory fit to
the observed MIDI visibilities of HR 5999 is found
with a model of a geometrically thin disk that is
truncated at 2.6 AU and seen under an inclination angle of
58 degr (i.e. closer to an edge-on view than to a face-on view).
Neither models of a
geometrically thin disk seen nearly edge-on, nor models of spherical dust
shells can achieve agreement between the observed and predicted visibilities.
The reason why the disk is so compact remains unclear;
we speculate that it has been truncated by a close binary companion.
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