Dynamical masses for the nearest brown dwarf binary: ɛ Indi Ba, Bb

Cardoso, C. V.; McCaughrean, M. J.; King, R. R.; Close, L. M.; Scholz, R.-D.; Lenzen, R.; Brandner, W.; Lodieu, N.; Zinnecker, H.
Bibliographical reference

COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP Conference Proceedings, Volume 1094, pp. 509-512 (2009).

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We present preliminary astrometric results for the closest known brown dwarf binary to the Sun: V Indi Ba, Bb at a distance of 3.626 pc. With ongoing monitoring of the relative separation of the two brown dwarfs (spectral types T1 and T6) with VLT NACO near-IR adaptive optics system since June 2004, we obtain a model-independent dynamical total mass for the system of 121 MJup, some 60% larger than the one obtained by McCaughrean et al., implying that the system may be as old as 5 Gyr. We have also been monitoring the absolute astrometric motions of the system using the VLTFORS2 optical imager since August 2005 to determine the individual masses. We predict a periastron passage in early 2010, by which time the system mass will be constrained to <1 MJup and we will be able to determine the individual masses accurately in a dynamical, model-independent manner.