Radial Velocities of Low-mass Candidate TWA Members

Abstract

Nearby young moving groups provide unique samples of similar age stars for testing the evolution of physical properties. Incomplete and/or incorrect group membership classifications reduce the usefulness of the group, which we assume to be coeval. With near-infrared spectra of two candidate members of the TW Hya Association, 2MASS J12354615−4115531 (TWA 46) and 2MASS J12371238−4021480 (TWA 47), we test their membership by adding radial velocity measurements to the literature. We find that 2MASS J12354615−4115531 is a close spectroscopic binary system with a center-of-mass radial velocity of −6.5 ± 3.9 km s −1 . This radial velocity and a Gaia parallax produces a TW Hydra association (TWA) membership probability of 41.9% using the Banyan Σ tool for 2MASS J12354615−4115531. The spectrum of 2MASS J12371238−4021480 shows that it appears to be a single star with a radial velocity consistent with the TW Hya Association and a membership probability of 99.5%. The reduced probability of TWA 46 as a true member of TWA highlights the importance of high-resolution, near-infrared spectra in validating low-mass moving group members.