The Smallest Mass Ratio Young Star Spectroscopic Binaries

Using high resolution near-infrared spectroscopy with the Keck telescope, wehave detected the radial velocity signatures of the cool secondary componentsin four optically identified pre-main-sequence, single-lined spectroscopicbinaries. All are weak-lined T Tauri stars with well-defined center of massvelocities. The mass ratio for one young binary, NTTS 160905-1859, is M2/M1 =0.18+/-0.01, the smallest yet measured dynamically for a pre-main-sequencespectroscopic binary. These new results demonstrate the power of infraredspectroscopy for the dynamical identification of cool secondaries. Visiblelight spectroscopy, to date, has not revealed any pre-main-sequence secondarystars with masses <0.5 M_sun, while two of the young systems reported here arein that range. We compare our targets with a compilation of the published youngdouble-lined spectroscopic binaries and discuss our unique contribution to thissample.Comment: Accepted for publication in the April, 2002, ApJ; 6 figure