J/A+A/510/A99 Epsilon Indi Ba and Bb IR spectra (King+, 2010)
Epsilon Indi Ba, Bb: a detailed study of the nearest known brown dwarfs.
King R.R., McCaughrean M.J., Homeier D., Allard F., Scholz R.-D., Lodieu N.
<Astron. Astrophys. 510, A99 (2010)>
=2010A&A...510A..99K 2010A&A...510A..99K
ADC_Keywords: Stars, nearby ; Spectra, infrared ; Spectra, red
Keywords: stars: atmospheres - stars: fundamental parameters -
stars: brown dwarfs - stars: individual: epsilon Indi B -
binaries: general - stars: late-type
Abstract:
The discovery of epsilon 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 epsilon Indi Ba, Bb
with the ESO VLT and present VRIzJHKL'M' broad-band photometry and
0.63-5.1 micron 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_☉=-4.699±0.017
and -5.232±0.020 for epsilon Indi Ba, Bb, respectively, and using
the dynamical system mass and COND03 evolutionary models predict a
system age of 3.7-4.3Gyr, in excess of previous estimates and recent
predictions from observations of these brown dwarfs. Moreover, the
effective temperatures of 1352-1385K and 976-1011K predicted from
the COND03 evolutionary models, for epsilon 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 1300-1340K and 880-940K, for
epsilon Indi Ba and Bb respectively, with surface gravities of
logg=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.
Description:
0.63-5.1 micron spectroscopy of the T dwarfs epsilon Indi Ba and Bb.
These observations were made with the ESO VLT ISAAC and FORS2
instruments. For each spectrum, the wavelength, flux, relative
uncertainty on the flux, and the uncertainty on the absolute flux
scale (from the photometric calibration) is given.
Objects:
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RA (2000) DE Designation(s) (SpType)
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22 04 10.6 -56 46 58 epsilon Indi Ba = * eps Ind Ba (T1)
22 04 10.6 -56 46 58 epsilon Indi Bb = * eps Ind Bb (T6)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 53 11 Flux ratio (Ba/Bb) of eps Indi Ba, Bb in the
observed FORS2 and ISAAC filters and derived
apparent magnitudes
sp/* . 2 Spectra of epsilon Indi Ba and epsilon Indi Bb
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See also:
J/other/ARA+A/43.195 : L and T dwarf stars (Kirkpatrick, 2005)
J/ApJ/648/629 : Radio observations of late M, L, and T dwarfs (Berger+, 2006)
J/ApJ/637/1067 : T dwarfs near-IR spectral classification (Burgasser+, 2006)
J/ApJ/651/502 : Spitzer IRAC photometry of M, L, and T dwarfs (Patten+, 2006)
J/AJ/133/971 : Low-mass stars & brown dwarfs wide companions (Allen+ 2007)
J/MNRAS/383/831 : New DENIS nearby L and late-M dwarfs (Phan-Bao+, 2008)
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Filt Filter name
9- 12 F4.2 --- FRatio ? Flux ratio (Ba/Bb) in band "Filt"
14- 17 F4.2 --- e_FRatio ? rms uncertainty on FRatio
19- 23 F5.3 um lam.eff ? Effective wavelength of filter "Filt"
25- 29 F5.3 um Dlam ? Half-power width of filter "Filt"
31- 35 F5.2 mag Bamag ? {elsilon} Indi Ba magnitude in filter "Filt"
37- 40 F4.2 mag e_Bamag ? rms uncertainty on Bamag
42- 43 A2 --- l_Bbmag [≥] Limit flag on Bbmag
44- 48 F5.2 mag Bbmag ? {elsilon} Indi Bb magnitude in filter "Filt"
50- 53 F4.2 mag e_Bbmag ? rms uncertainty on Bamag
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 10 F10.4 0.1nm lambda Wavelength
11- 25 E15.4 W/m2/um Flux Flux (Flambda)
26- 40 E15.4 W/m2/um e_Flux Relative uncertainty on flux
41- 55 E15.4 W/m2/um eFlux Absolute uncertainty on flux
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Acknowledgements:
Robert King,
(End) Patricia Vannier [CDS] 20-Oct-2009