2011A&A...533A..89G

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. 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. We spatially resolve the transitional disk around GM Aur and determine an inner-disk hole radius of 20.5^+1.0_–0.5AU. The circumstellar disks around DHTau and DMTau are not spatially resolved but we are able to constrain the inner-disk hole radius to <15.5^+9.0_–2.0AU and <15.5^+0.5_–0.5AU, respectively. The performed photometry yields fluxes of 178±31mJy for DHTau, 56±6mJy for DMTau, and 229±14mJy for GM Aur.