| This work describes an investigation of the astrophysics and accretion disk evolution in the spatially resolved components of close, pre-main-sequence binary stars. Combining near-IR spectroscopy and photometry, I have determined the spectral types, luminosities, masses, ages, Aυs and near-IR excesses for 29 stars in 16 binary systems (0.3–7.6"), and the mass ratios for 12 such systems. Typical masses range from 0.1–0.4 and mass ratios, M1/M 2, from ∼1–3.; In an overlapping sample of 25 systems, I observed evidence for circumstellar disks around both stars in 15 systems and around neither star in 5 systems. The stars in the remaining 5 systems show evidence for disks in only one component. This is usually the primary star, however, in one case it is the secondary. These results are consistent with the current models for binary star formation by fragmentation.; I have also begun a program to determine dynamical masses and mass ratios in pre-main-sequence single-lined spectroscopic binaries. For the single-lined spectroscopic binary NTT 155913–2233, 1 have identified the spectrum of the cool M5 secondary. The mass ratio, M1/ M2, is 2.1, the largest yet measured for a premain-sequence spectroscopic system. The temperature, mass ratio, lower mass limits and assumed coevality of this 2.4 day period system impose potentially useful constraints on the calibration of the pre-main-sequence evolutionary tracks. |
