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G. Doppmann (Gemini Observatory), R. White (Caltech), D. Charbonneau (Harvard)
Empirical measurements of basic stellar and substellar properties in pre-main sequence (PMS) objects are critical to our understanding of how and when these objects evolve toward the main sequence. Dynamical measurements of PMS binary systems are beginning to provide these fundamental data, if they can be accurately placed on an H-R diagram for comparison with PMS evolutionary models. A recent high-precision near-IR radial velocity survey with Phoenix at Gemini South has lead to the new discovery of one double-line spectroscopic binary in Chamaeleon. With the high spectral resolution (R=50,000) provided by Phoenix we have successfully measured the orbital period and determined the dynamical mass ratio (from the relative velocity amplitudes) with our spectra taken over nine epochs (29 April - 23 June, 2005). In two epochs where we have near maximum velocity separation at the 2-0 CO bandhead, we use spectral synthesis templates to fit the primary and secondary bandheads (both evident in the spectrum) to accurately determine the component spectral types. Our multicomponent spectral fits also set constraints on gravity, assumed to be equal for both components in this low mass (~M2) co-evol PMS binary system. With the placement of this system in the H-R diagram by the properties we determine from spectroscopy, we will test the accuracy of theoretical model tracks using the independent mass information obtained from the orbital motion.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.