Mid-infrared imaging of the young binary star Hen 3-600: Evidence for a dust disk around the primary

We present high-resolution mid-infrared observations of the nearby late-typ e young binary system Hen 3-600. The binary, at a distance of similar to 50 pc, could be a member of the TW Hydrae association, the nearest known grou p of young stars, with an age of a few million years. Our images make it po ssible for the first time to determine which star in the pair, separated by 1." 4, harbors the mid-infrared excess detected by IRAS. In the near-infra red, where the radiation is primarily photospheric, Hen 3-600A (M3) and Hen 3-600B (M3.5) have a flux ratio of 1.6. At 4.8, 10.8, and 18.2 mu m, the p rimary becomes increasingly dominant over the secondary, suggesting that mo st of the circumstellar dust in the system resides around Hen 3-600A. Compa rison of the spectral energy distribution (SED) of Hen 3-600A to the median SED of classical T Tauri stars suggests that its disk may be truncated by the secondary and provides tentative evidence for a central disk hole. The distribution of dust in the Hen 3-600 system may provide important clues to the formation and evolution of protoplanetary disks in close binaries.