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Because of their high luminosity and distinctive optical spectra, carbon stars can be used as kinematic probes of the Galaxy to great distances (Bothun et al., 1991, Astron. J., 101, 2220). However, a number of faint carbon stars at high galactic latitudes (including three from the above work) show significant proper motion, suggesting a main-sequence luminosity. These carbon dwarf (dC) stars are generally believed to be binary systems in which the main-sequence dwarf has received processed material from a now invisible companion during the companion's ascent of the AGB. The optical spectra of dwarf and giant carbon stars are similar, and unambiguous discriminants such as proper motion can be problematic. Infrared spectra of a selection of faint carbon stars in the J, H, and K bands indicate that known dC stars have weak first-overtone CO bands by comparison to known carbon giants. This supports the suggestion of Green et al. (1991, Ap. J. Lett., 380, L31) that infrared colors may provide a useful luminosity discriminant.
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