Young Binary Stars in Taurus-Auriga

We present the results of a high spatial resolution ultraviolet, optical and near-infrared survey of 44 young binary stars in Taurus-Auriga with separations of 10–1000 AU. The observations were carried out using the Hubble Space Telescope and NASA's IRTF. The binary star properties corroborate our previous work that suggests fragmentation is the dominant binary star formation mechanism. Of particular interest, we find that the components of binary systems are more coeval than randomly paired single T Tauri stars. Several important conclusions are drawn regarding the evolution of circumstellar material in binary systems. The mass accretion rates for primary stars are similar to single stars, which suggests that a companion as close as 10 AU has little effect on the mass accretion rate. These accretion rates, if constant, require replenishment of the inner circumstellar disks for at least the closest (≲ 100 AU) binary systems. On average, circumprimary disks appear to survive longer and accrete at a higher rate than circumsecondary disks do. This suggests that circumprimary disks are being preferentially replenished, possibly from a circumbinary reservoir with low angular momentum relative to the binary. The relative T Tauri types and the binary mass ratios tentatively suggest that systems with separations ≲ 200 AU share a common circumbinary reservoir. The higher mass accretion rates of primary stars relative to secondary stars is most likely due to their larger relative mass.