Ophiuchus 1622−2405: Not a Planetary‐Mass Binary

Abstract

We present an analysis of the mass and age of the young low-mass binary Oph 1622-2405. Using resolved optical spectroscopy of the binary, we measure spectral types of M7.25+/-0.25 and M8.75+/-0.25 for the A and B components, respectively. We show that our spectra are inconsistent with the spectral types of M9 and M9.5-L0 from Jayawardhana & Ivanov and M9+/-0.5 and M9.5+/-0.5 from Close and coworkers. Based on our spectral types and the theoretical evolutionary models of Chabrier and Baraffe, we estimate masses of ~0.055 and ~0.019 Msolar for Oph 1622-2405A and B, which are significantly higher than the values of 0.013 and 0.007 Msolar derived by Jayawardhana & Ivanov and above the range of masses observed for extrasolar planets (M 1 Gyr) and members of Taurus (τ~1 Myr) and Upper Scorpius (τ~5 Myr). The line strengths for Oph 1622-2405A are inconsistent with membership in Ophiuchus (τ<1 Myr) and instead indicate an age similar to that of Upper Sco, which is in agreement with a similar analysis performed by Close and coworkers. We conclude that Oph 1622-2405 is part of an older population in Sco-Cen, perhaps Upper Sco itself. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory Chile.