J/A+A/686/A37 X-Shooter spectra of young LT dwarfs (Piscarreta+, 2024)
Spectral characterization of young LT dwarfs.
Piscarreta L., Muzic K., Almendros-Abad V., Scholz A.
<Astron. Astrophys. 686, A37 (2024)>
=2024A&A...686A..37P 2024A&A...686A..37P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Spectroscopy ; Spectra, infrared
Keywords: techniques: spectroscopic - brown dwarfs
Abstract:
JWST and next-generation facilities are expected to uncover
populations of free-floating objects below the deuterium-burning limit
in a number of young clusters and star-forming regions. These young
planetary-mass brown dwarfs have spectral types L and T; they are
shaped by molecular absorption and modified by their low gravity,
which makes them distinct from field objects.
We aim to provide a detailed characterization of near-infrared spectra
for young LT brown dwarfs, including robust spectral typing,
calibrating spectral indices, identifying possible binaries, and
selecting suitable spectral standards.
We processed and analyzed archival spectra from VLT/X-shooter for a
sample of 56 dwarfs with ages between 10 and 600Myr and spectral
types between late-M and mid-T. We re-determine spectral types by
comparing them with a set of literature templates and assess a large
range of spectral indices, calibrated using a specifically designed
literature sample. We are able to identify 15 spectral indices that
are useful for spectral typing for specific spectral ranges discussed
here and provide the scaling relations with spectral types. Moreover,
we also identify 6 spectral indices which can be used to separate
young L dwarfs from the field ones.
The equivalent-widths of the alkali lines show a correlation with age,
increasing towards the objects with higher surface gravity. From our
sample, we confirm 3 that are likely to be binaries by their anomalous
spectra that appear to be better fitted by a combination of spectral
types.
Finally, we identify 12 objects as preliminary near-infrared spectral
standards for young LT dwarfs. This paper presents a significant step
toward understanding the spectral sequence and properties of young L
and T dwarfs. The relations and standards provided here will be useful
for future spectroscopic work on young brown dwarfs and giant planets.
Description:
Reduced, flux-calibrated and telluric-corrected 1D X-Shooter NIR
spectra of the 56 objects considered in this work.
The spectra are given in fits format and are not corrected for
extinction.
The wavelength is in nanometers and the flux in erg/s/cm^2/Å.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 106 56 List of sources
fits/* . 56 Individual fits 1D X-Shooter NIR spectra
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- ID [2/63] Source ID
4- 28 A25 --- Name Source name
30- 31 I2 h RAh Right ascension (J2000)
33- 34 I2 min RAm Right ascension (J2000)
36- 40 F5.2 s RAs Right ascension (J2000)
42 A1 --- DE- Declination sign (J2000)
43- 44 I2 deg DEd Declination (J2000)
46- 47 I2 arcmin DEm Declination (J2000)
49- 52 F4.1 arcsec DEs Declination (J2000)
54- 58 A5 --- Region Region to which each source belongs
60- 63 A4 --- SpType Spectral type
65- 67 F3.1 --- E_SpType ? Upper bound uncertainty on the SpType
69- 71 F3.1 --- e_SpType ? Lower bound uncertainty on the SpType
73- 77 A5 --- TempSet Set of templates used for the SpType derivation
79- 81 F3.1 mag Av ?=- Visual extinction
83-106 A24 --- FileName Spectrum file name in subdirectory fits
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Acknowledgements:
Lara Piscarreta, lara.alvopiscarreta(at)eso.org
(End) Patricia Vannier [CDS] 11-Mar-2024