Preliminary Physical Orbit of the HD 98800 B System

As a part of a larger program to measure physical properties of PMS binary systems, we have observed the PMS quadruple system HD 98800 (aka TW Hya 4A) with the Keck Interferometer (KI), and resolved the two separate spectroscopic binary components of the system. In particular we have observed the HD 98800 North (B) binary component on multiple epochs, and integrating our data with the double-lined spectroscopic orbit from Torres et al [15] has allowed us to estimate a physical orbit for the B system. This orbit in turn yields relatively accurate (8%) mass estimates of the component stars, and an independent system distance and component luminosity estimates. Comparisons between the estimated physical parameters for the low-mass HD 98800 B components with mass-luminosity models of PMS stars, and implications for the age of HD 98800 are discussed.