The Orbit of the Nearby Low-Mass Binary Gliese 600

Abstract

We have computed a combined spectroscopic-interferometric orbit for the nearby binary Gliese 600 discovered by us. The orbital period is 2.78 years, and the semimajor axis is 100 mas (0.1"). Its M0V components are almost identical and have a mass of 0.5 M_solar. The mass ratio is uncertain because of the low radial-velocity semiamplitude (7 km/s) associated with the low orbital inclination (37°deg). The orbital parallax of the binary (52 +/- 11 mas) matches its dynamical and photometric parallaxes but differs significantly from the HIPPARCOS parallax (44.3 +/- 1.6 mas); the latter was probably distorted by the orbital motion that was not taken into account.