A HIGH-PRECISION NEAR-INFRARED SURVEY FOR RADIAL VELOCITY VARIABLE LOW-MASS STARS USING CSHELL AND A METHANE GAS CELL

We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA InfraRed Telescope Facility in the K band with an isotopologue methane gas cell to achieve wavelength calibration and a novel, iterative RV extraction method. We surveyed 14 members of young (approximate to 25-150 Myr) moving groups, the young field star epsilon. Eridani, and 18 nearby (< 25 pc) low-mass stars and achieved typical single-measurement precisions of 8-15 m s(-1) with a long-term stability of 15-50 m s(-1) over longer baselines. We obtain the best NIR RV constraints to date on 27 targets in our sample, 19 of which were never followed by high-precision RV surveys. Our results indicate that very active stars can display long-term RV variations as low as similar to 25-50 m s(-1) at approximate to 2.3125 mu m, thus constraining the effect of jitter at these wavelengths. We provide the first multiwavelength confirmation of GJ. 876. bc and independently retrieve orbital parameters consistent with previous studies. We recovered RV variabilities for HD. 160934. AB and GJ. 725. AB that are consistent with their known binary orbits, and nine other targets are candidate RV variables with a statistical significance of 3s-5s. Our method, combined with the new iSHELL spectrograph, will yield long-term RV precisions of. 5 m s(-1) in the NIR, which will allow the detection of super-Earths near the habitable zone of mid-M dwarfs.