Atmospheric Analysis of the M / L – and M / T – Dwarf Binary Systems LHS 102 and Gliese 229

We present 0.9—2.5μm spectroscopy with R∼800 and 1.12-1.22μm spectroscopy with R∼5800 for the M dwarfs Gl 229A and LHS 102A, and for the L dwarf LHS 102B. We also report IZJHKL′ photometry for both components of the LHS 102 system, and L′ photometry for Gl 229A. The data are combined with previously published spectroscopy and photometry to produce flux distributions for each component of the kinematically old disk M/L–dwarf binary system LHS 102 and the kinematically young disk M/T–dwarf binary system Gliese 229. The data are analyzed using synthetic spectra generated by the latest “AMES-dusty” and “AMES-cond” models by Allard & Hauschildt. Although the models are not able to reproduce the overall slope of the infrared flux distribution of the L dwarf, most likely due to the treatment of dust in the photosphere, the data for the M dwarfs and the T dwarf are well matched. We find that the Gl 229 system is metal–poor despite having kinematics of the young disk, and that the LHS 102 system has solar metallicity. The observed luminosities and derived temperatures and gravities are consistent with evolutionary model predictions if the Gl 229 system is very young (age ∼ 30 Myr) with masses (A,B) of (0.38,∼> 0.007)M , and the LHS 102 system is older, aged 1—10 Gyr with masses (A,B) of (0.19,0.07)M .