Cátia Cardoso
University of Exeter, UK

Abstract
We present new preliminary astrometric results for the closest known brown dwarf binary to Earth, ε Indi Ba, Bb at a distance of 3.6224 pc. The relative orbital motion of the brown dwarfs (spectral types T1 and T6) has been monitored since June 2004 with the VLT NACO near-IR adaptive optics system. With data for more than half the orbit now, we obtain an accurate total dynamical system mass (<1%), considerably in excess of earlier determinations based on evolutionary models. We have also been monitoring the absolute astrometric motion of the system since August 2005 against a network of field stars using the VLT FORS2 optical imager with the aim of determining the individual masses. Our current orbit solution predicts periastron passage in early 2010, and shortly thereafter, we should be able to determine the absolute masses to better than 5% in a model independent way.

2009 December 16, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
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