Constraints on disk sizes around young intermediate-mass stars: Nulling interferometric observations of Herbig Ae objects

Physical models of circumstellar disks surrounding pre-main-sequence stars are currently constrained primarily by the spectral energy distribution of the system. Here we present first results from a survey of nearby Herbig Ae stars using nulling interferometry. We measure the spatial extent of the mid-IR emission for the stars HD 150193, HD 163296, and HD 179218. The results indicate that the size of mid-IR emission around Herbig Ae stars may be much smaller than current models predict. The observations constrain similar to 90% of the 10 mum flux to be within an approximately 20 AU diameter region, providing significant spatial limits for disk models. These results demonstrate the scientific potential for nulling interferometry to study circumstellar disks with better spatial discernment than is possible with standard mid-IR imaging.