AAS 198th Meeting, June 2001
Session 18. Protostellar Disks
Oral, Monday, June 4, 2001, 10:00-11:30am, C104

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[18.04] Resolved near-infrared spectroscopy of the 75 milliarcsecond PMS binary T Tau South

G. Duchene, A. Ghez, C.-E. McCabe (UCLA)

We present the first resolved near-infrared spectra of T Tau South, a 75 milliarcsecond (10 AU) pre-main sequence binary system located only 0.7'' away from the archetype classical T Tauri star, T Tau North. Considered globably, this system has been extensively studied for several years because of its extremely red color, which placed it in the "infrared companion" category. Among its previously known features, the most striking ones are the absence of any photopheric spectral feature and a strong photometric variability.

The very high spatial resolution allowed by the adaptive optics system at Keck allows us to clearly resolve this very tight system. In this contribution, we present new imaging and spectroscopic measurements of T Tau South obtained in November 2000 with NIRSPEC behind the adaptive optics bench. The H-band and K-band images extend the baseline for time variability studies of the system; at least one of the two stars in this system is variable.

Our low resolution (R=2000) K-band spectra confirm that T Tau South A displays no identifiable feature, with the only exception of Br\gamma seen in emission, and reveal for the first time some photospheric features from T Tau South B. Several CO bandheads, the Ca triplet and Na doublet are identified, suggesting an early-G spectral type if the star does not present significant accretion-induced near-infrared excess emission. We also find that the secondary has a larger Br\gamma emission equivalent width than the primary.

We also obtained high resolution (R=30000) H-band spectra of the binary in order to derive the radial velocity of the two stars. These figure will be ultimately combined with astrometric measurements to derive orbital parameters and, hence, both stellar masses. We present here some preliminary results showing the efficiency of the method.

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