A nearby young M dwarf with a wide, possibly planetary-mass companion

作者：Deacon N R^*; Schlieder J E; Murphy S J

来源：Monthly Notices of the Royal Astronomical Society, 2016, 457(3): 3191-3199.

DOI：10.1093/mnras/stw172

• planets and satellites: detection
• binaries: visual
• brown dwarfs
• stars: pre-main-sequence

We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the similar to 45 Myr old Tucana-Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708 angstrom absorption consistent with M dwarfs younger than TucHor but older than the similar to 10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the similar to 24 Myr old beta Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6-15 M-I for the secondary. It is thus likely 2MASS J2126-8140 is the widest orbit planetary-mass object known (>4500 au) and its estimated mass, age, spectral type, and T-eff are similar to the well-studied planet beta Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.

• 出版日期2016-4-11