43 Brown Dwarf Systems Observed, 3 Binary Brown Dwarf Systems Resolved

High Resolution Imaging of Very Low Mass Spectral Binaries: Three Resolved Systems and Detection of Orbital Motion in an L/T Transition Binary

Authors:

Bardalez Gagliuffi et al

Abstract:

We present high resolution Laser Guide Star Adaptive Optics imaging of 43 late-M, L and T dwarf systems with Keck/NIRC2. These include 17 spectral binary candidates, systems whose spectra suggest the presence of a T dwarf secondary. We resolve three systems: 2MASS J1341−3052, SDSS J1511+0607 and SDSS J2052−1609; the first two are resolved for the first time. All three have projected separations less than 8 AU and estimated periods of 14−80 years. We also report a preliminary orbit determination for SDSS J2052−1609 based on six epochs of resolved astrometry between 2005−2010. Among the 14 unresolved spectral binaries, 5 systems were confirmed binaries but remained unresolved, implying a minimum binary fraction of 47+12−11% for this sample. Our inability to resolve most of the spectral binaries, including the confirmed binaries, supports the hypothesis that a large fraction of very low mass systems have relatively small separations and are missed with direct imaging.