AB Doradus C: age, spectral type, orbit, and comparison to evolutionary models

Abstract

We expand upon the results of Close et al. (2005) regarding the young, low-mass object AB Dor C and its role as a calibration point for theoretical tracks. We present an improved spectral reduction and a new orbital solution with two additional epochs. Our improved analysis confirms our spectral type of M8 (±1) and mass of 0.090 ±0.003 M\sun for AB Dor C. Comparing the results for AB Dor C with other young, low-mass objects with dynamical masses we find a general trend where current evolutionary models tend to over-predict the temperature (or under-predict the mass) for low-mass stars and brown dwarfs. Given our precision, there is a ∼99% chance that the mass of AB Dor C is underestimated by the DUSTY tracks in the HR diagram.