Bibcode
King, R. R.; McCaughrean, M. J.; Homeier, D.; Allard, F.; Scholz, R.-D.; Lodieu, N.
Bibliographical reference
Astronomy and Astrophysics, Volume 510, id.A99
Advertised on:
2
2010
Journal
Citations
79
Refereed citations
69
Description
The discovery of ɛ Indi Ba, Bb, a binary brown dwarf system very
close to the Sun, makes possible a concerted campaign to characterise
the physical parameters of two T dwarfs. Recent observations suggest
substellar atmospheric and evolutionary models may be inconsistent with
observations, but there have been few conclusive tests to date. We
therefore aim to characterise these benchmark brown dwarfs to place
constraints on such models. We have obtained high angular resolution
optical, near-infrared, and thermal-infrared imaging and
medium-resolution (up to R ~ 5000) spectroscopy of ɛ Indi Ba, Bb
with the ESO VLT and present VRIzJHKL'M' broad-band photometry and
0.63-5.1 μm spectroscopy of the individual components. The photometry
and spectroscopy of the two partially blended sources were extracted
with a custom algorithm. Furthermore, we use deep AO-imaging to place
upper limits on the (model-dependent) mass of any further system
members. We derive luminosities of log L/L&sun; = -4.699
±0.017 and -5.232 ±0.020 for ɛ Indi Ba, Bb,
respectively, and using the dynamical system mass and COND03
evolutionary models predict a system age of 3.7-4.3 Gyr, in excess of
previous estimates and recent predictions from observations of these
brown dwarfs. Moreover, the effective temperatures of 1352-1385 K and
976-1011 K predicted from the COND03 evolutionary models, for ɛ
Indi Ba and Bb respectively, are in disagreement with those derived from
the comparison of our data with the BT-Settl atmospheric models where we
find effective temperatures of 1300-1340 K and 880-940 K, for ɛ
Indi Ba and Bb respectively, with surface gravities of log g = 5.25 and
5.50. Finally, we show that spectroscopically determined effective
temperatures and surface gravities for ultra-cool dwarfs can lead to
underestimated masses even where precise luminosity constraints are
available.
Based on observations collected with the ESO VLT, Paranal, Chile under
program 072.C-0689
The full resolution spectra of both brown dwarfs are only available in
electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/510/A99