A search for spectroscopic binaries among very low-mass stars and brown dwarfs

This project is a search for spectroscopic binaries (SB) among very low-mass stars and brown dwarfs. As a pioneering effort, we are reobserving the more than 60 stars studied by Mohanty & Basri 2003 to look for radial velocity variability using the HIRES echelle on Keck. We use the same settings as the original epoch, so that the problem becomes one of just finding the relative shift of the stellar signal. We use the night sky as a reference. Sensitivity to 300 m/s brings us out to the minimum separations that AO or HST can uncover (the objects are generally less than 20 pc distant). Thus far, it appears that the number of SB is comparable to G-dwarfs at small separations, pointing towards a cut-off at wide separations rather than a compressed distribution.