EVIDENCE FOR DUST AROUND POST T-TAURI STARS

Post T Tauri stars are young stars which, although older than classical T Tauri stars, have not yet reached the main sequence. We report the detection of a far-infrared excess in binary systems consisting of a post T-Tauri secondary and a B-type primary. Assuming this excess arises from dust surrounding the secondary, it is not clear whether the primary or the secondary, i.e., the post T Tauri star, is the dominant heating source. We searched for continuum 1.1 mm emission in a small sample of candidate (or confirmed) post T Tauri and post Herbig Ae/Be stars with the Caltech Submillimeter Observatory. In no case did we detect any emission. The inferred upper limits to the amount of dust present is typically one or two orders of magnitude lower than that found around classical T Tauri/Herbig Ae/Be stars suggesting rapid evolution of the disk before a star reaches the post T Tauri/Herbig Ae/Be phase.