The Nearby Young Visual Binary HIP 115147 and Its Common Proper Motion Companion LSPM J2322+7847

Abstract

We report a late M-type, common proper motion companion to a nearby young visual binary HIP 115147 (V368 Cep), separated by 963" from the primary K0 dwarf. This optically dim star was identified as a candidate high proper motion, nearby dwarf LSPM J2322+7847 by Lépine in 2005. The wide companion is one of the latest post-T Tauri low-mass stars found within 20 pc. We obtain a trigonometric parallax of 51.6+/-0.8 mas, in good agreement with the Hipparcos parallax of the primary star (50.7+/-0.6 mas). Our BVRI photometric data and near-infrared data from 2MASS are consistent with LSPM J2322+7847 being brighter by 1 mag in K_s than field M dwarfs at V-K_s=6.66, which indicates its pre-main-sequence status. We conclude that the most likely age of the primary HIP 115147 and its 11" companion HIP 115147B is 20-50 Myr. The primary appears to be older than its close analog PZ Tel (age 12-20 Myr) and members of the TWA association (7 Myr).