STScI Preprint #1196
Based on observations obtained with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Aeronautics and Space Administration.\morethanksBased on data from the ESA Hipparcos astrometry satellite.\morethanksBased on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology.
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 paper we present new astrometric observations made with Hipparcos as well as photometry from Hubble Space Telescope WFPC2 images. Combining these observations and reanalyzing previous work allows us to estimate the age and masses of the stars in the system. Uncertainty in these ages and masses results from uncertainty in the temperatures of the stars and any reddening they may have. We find that HD 98800 is most probably about 10 Myr old, although it may be as young as 5 Myr or as old as 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 post-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 98800 may have formed in the Centaurus star-forming region, but it is extraordinary in being so young and yet so far from where it was born.