HD-98800 - A UNIQUE STELLAR SYSTEM OF POST-T TAURI STARS

HD 98800 is a system of four stars, and it has a large infrared excess that is thought to be due to a dust disk within the system. In this p aper we present new astrometric observations made with Hipparcos, as w ell as photometry from Hubble Space Telescope WFPC2 images. Combining these observations and reanalyzing previous work allow us to estimate the age and masses of the stars in the system. Uncertainty in these ag es and masses results from uncertainty in the temperatures of the star s and any reddening they may have. We find that HD 98800 is most proba bly about 10 Myr old, although it may be as young as 5 Myr or as old a s 20 Myr. The stars in HD 98800 appear to have metallicities that are about solar. An age of 10 Myr means that HD 98800 is a member of the p ost-T Tauri class of objects, and we argue that the stars in HD 98800 can help us understand why post-T Tauris have been so elusive. HD 9880 0 may have formed in the Centaurus star-forming region, but it is extr aordinary in being so young and yet so far from where it was born.