HD 98800: A Unique Stellar System of Post–T Tauri Stars

Abstract

HD 98800 is a system of four stars, and it has a large infrared excessthat is thought to be due to a dust disk within the system. In thispaper we present new astrometric observations made with Hipparcos,as well as photometry from Hubble Space Telescope WFPC2 images. Combiningthese observations and reanalyzing previous work allow us to estimatethe age and masses of the stars in the system. Uncertainty in theseages and masses results from uncertainty in the temperatures of thestars and any reddening they may have. We find that HD 98800 is mostprobably about 10 Myr old, although it may be as young as 5 Myr oras old as 20 Myr. The stars in HD 98800 appear to have metallicitiesthat are about solar. An age of 10 Myr means that HD 98800 is a memberof the post-T Tauri class of objects, and we argue that the starsin HD 98800 can help us understand why post-T Tauris have been soelusive. HD 98800 may have formed in the Centaurus star-forming region,but it is extraordinary in being so young and yet so far from whereit was born.