Volume 413, Number 3, January III 2004
|Page(s)||1029 - 1036|
|Section||Stellar structure and evolution|
|Published online||07 January 2004|
ε Indi Ba,Bb: The nearest binary brown dwarf*
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
2 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721–0065, USA
3 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
4 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
Corresponding author: M. J. McCaughrean, email@example.com
Accepted: 2 October 2003
We have carried out high angular resolution near-infrared imaging and low-resolution () spectroscopy of the nearest known brown dwarf, ε Indi B, using the ESO VLT NAOS/CONICA adaptive optics system. We find it to be a close binary (as also noted by Volk et al. 2003), with an angular separation of 0.732 arcsec, corresponding to 2.65 AU at the 3.626 pc distance of the ε Indi system. In our discovery paper (Scholz et al. 2003), we concluded that ε Indi B was a ~50 MJup T2.5 dwarf: our revised finding is that the two system components (ε Indi Ba and ε Indi Bb) have spectral types of T1 and T6, respectively, and estimated masses of 47 and 28 MJup , respectively, assuming an age of 1.3 Gyr. Errors in the masses are ±10 and ±7 MJup , respectively, dominated by the uncertainty in the age determination (0.8–2 Gyr range). This uniquely well-characterised T dwarf binary system should prove important in the study of low-mass, cool brown dwarfs. The two components are bright and relatively well-resolved: ε Indi B is the only T dwarf binary in which spectra have been obtained for both components. The system has a well-established distance and age. Finally, their orbital motion can be measured on a fairly short timescale (nominal orbital period ~15 yrs), permitting an accurate determination of the true total system mass, helping to calibrate brown dwarf evolutionary models.
Key words: astrometry / surveys / stars: late-type / stars: low mass, brown dwarfs / stars: binaries: general
© ESO, 2004
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.