Thursday, July 11, 2013

1307.2722 (Gabriel Bihain et al.)

An overlooked brown dwarf neighbour (T7.5 at d~5pc) of the Sun and two further T dwarfs at about 10pc    [PDF]

Gabriel Bihain, Ralf-Dieter Scholz, Jesper Storm, Olivier Schnurr
Although many new brown dwarf (BD) neighbours have been recently discovered thanks to new sky surveys in the mid- and near-infrared (MIR, NIR), their numbers are still more than five times lower than those of stars in the same volume. We aim at detecting and classifying new BDs to eventually complete their census in the immediate Solar neighbourhood. We combine multi-epoch data from sky surveys at different wavelengths to detect BD neighbours of the Sun by their high proper motion (HPM). We concentrate at relatively bright MIR (w2<13.5) BD candidates from WISE expected to be so close to the Sun that they may also be seen in older NIR (2MASS, DENIS) or even red optical (SDSS i- and z-band, SSS I-band) surveys. With low-resolution NIR spectroscopy we classify the new BDs and estimate their distances and velocities. We have discovered the HPM (pm~470mas/yr) T7.5 dwarf WISE J0521+1025 at d=5.0+-1.3pc from the Sun, and two early-T dwarfs WISE J0457-0207 (T2) and WISE J2030+0749 (T1.5) with proper motions of ~120 and ~670mas/yr and distances of 12.5+-3.1pc and 10.5+-2.6pc, respectively. All three show thin disk kinematics. They may have been overlooked in the past due to overlapping images and problems with matching objects between different surveys and measuring their proper motions.
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