J/A+A/564/A55 1.1-2.4um spectra of 7 young M and L dwarfs (Manjavacas+, 2014)
New constrains on the formation and settling of dust in the atmospheres of
young M and L dwarfs.
Manjavacas E., Bonnefoy M., Schlieder J.E., Allard F., Rojo P., Goldman B.,
Chauvin G., Homeier D., Lodieu N., Henning T.
<Astron. Astrophys. 564, A55 (2014)>
=2014A&A...564A..55M 2014A&A...564A..55M
ADC_Keywords: Stars, dwarfs ; Stars, late-type ; Spectroscopy
Keywords: stars: low-mass - brown dwarfs - planetary systems -
techniques: spectroscopic
Abstract:
Gravity modifies the spectral features of young brown dwarfs (BDs). A
proper characterization of these objects is crucial for the
identification of the least massive and latest-type objects in
star-forming regions, and to explain the origin(s) of the peculiar
spectrophotometric properties of young directly imaged extrasolar
planets and BD companions.
We obtained medium-resolution (R∼1500-1700) near-infrared (1.1-2.5um)
spectra of seven young M9.5-L3 dwarfs classified at optical
wavelengths. We aim to empirically confirm the low surface gravity of
the objects in the near-infrared. We also test whether self-consistent
atmospheric models correctly represent the formation and the settling
of dust clouds in the atmosphere of young late-M and L dwarfs.
We used the Infrared Spectrometer And Array Camera (ISAAC) at the Very
Large Telescope (VLT) to obtain the spectra of the targets. We
compared the spectra to those of mature and young BDs, and to young
late-type companions to nearby stars with known ages, to identify and
study gravity-sensitive features. We computed spectral indices weakly
sensitive to the surface gravity to derive near-infrared spectral
types. Finally, we found the best fit between each spectrum and
synthetic spectra from the BT-Settl 2010 and 2013 atmospheric models.
Using the best fit, we derived the atmospheric parameters of the
objects and identified which spectral characteristics the models do
not reproduce.
Description:
Our targets were observed with the Infrared Spectrometer And
Array Camera (ISAAC) mounted on the Very Large Telescope (VLT) ath the
UT3 telescope. The instrument was operated in low-resolution mode with
the 0.3" slit at central wavelengths 1.25um, 1.65um, and 2.2um. This
setup provides spectra with resolving powers of ∼1700, 1600, and
1500 from 1.1-1.4um (J band), 1.42-1.82um (H band), and 1.82-2.5um
(K band).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 86 7 List of studied objects
sp/* . 7 Individual FITS spectra
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Name Object name
26- 27 I2 h RAh Right ascension (J2000)
29- 30 I2 min RAm Right ascension (J2000)
32- 35 F4.1 s RAs Right ascension (J2000)
37 A1 --- DE- Declination sign (J2000)
38- 39 I2 deg DEd Declination (J2000)
41- 42 I2 arcmin DEm Declination (J2000)
44- 45 I2 arcsec DEs Declination (J2000)
47- 86 A40 --- FileName Name of the FITS file in subdirectory sp
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Acknowledgements:
Elena Manjavacas, manjavacas(at)mpia.de
(End) Patricia Vannier [CDS] 20-Feb-2014