Aims: We present mid-infrared observations and photometry of the transitional
disks around the young stellar objects DH Tau, DM Tau, and GM Aur, obtained
with VISIR/VLT in N band. Our aim is to resolve the inner region and the
large-scale structures of these transitional disks, carrying potential
signatures of intermediate or later stages of disk evolution and ongoing planet
formation.
Methods: We use the simultaneously observed standard-stars as PSF reference
to constrain the radial flux profiles of our target objects. Subtracting the
obtained standard-star profile from the corresponding science object profile
yields the flux residuals produced by the star-disk system. A detection
threshold takes into account the background standard deviation and also the
seeing variations during the observations to evaluate the significance of these
flux residuals. On the basis of a simple model for the dust re-emission, we
derive constraints on the inner radius of the dust disk.
Results: We spatially resolve the transitional disk around GM Aur and
determine an inner-disk hole radius of 20.5(+1.0,-0.5) AU. The circumstellar
disks around DH Tau and DM Tau are not spatially resolved but we are able to
constrain the inner-disk hole radius to <15.5(+9.0,-2.0) AU and
<15.5(+0.5,-0.5) AU, respectively. The performed photometry yields fluxes of
178+-31 mJy for DH Tau, 56+-6 mJy for DM Tau, and 229+-14 mJy for GM Aur.Comment: Accepted for publication in Astronomy & Astrophysics. (6 pages,
including 7 figures and 5 tables