2014A&A...568A...6Z


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.22CEST11:57:46

2014A&A...568A...6Z - Astronomy and Astrophysics, volume 568A, 6-6 (2014/8-1)

Trigonometric parallaxes of young field L dwarfs.

ZAPATERO OSORIO M.R., BEJAR V.J.S., MILES-PAEZ P.A., PENA RAMIREZ K., REBOLO R. and PALLE E.

Abstract (from CDS):

We aim to determine the trigonometric parallaxes and proper motions of a sample of ten field L0-L5 dwarfs with spectroscopic evidence for low-gravity atmospheres. The ten sources were located in color-absolute magnitude diagrams and in the Hertzsprung-Russell (HR) diagram for age and mass derivations and were compared with field and star cluster dwarfs of related spectral classification and with state-of-the-art solar-metallicity evolutionary models. We obtained J and Ks imaging data using 2-4m class telescopes with a typical cadence of one image per month between 2010 January and 2012 December, in which the data cover a time baseline of nearly three years. We also obtained low resolution optical spectra (R ∼300, 500-1100nm) using the 10m Gran Telescopio de Canarias to assess the presence of lithium absorption in four targets and confirm their young age. The derived parallaxes and proper motions were combined with data from the literature to determine Teff, luminosity, and space velocities. All this information along with the lithium observations was used to assess the ages and masses of the sample. The astrometric curves were also examined for periodic perturbations indicative of unseen companions. Trigonometric parallaxes and proper motions were derived to typical accuracies of a milliarcsecond (mas) and ±10mas/yr, respectively. All ten L dwarfs have large motions (µ≥70mas/yr) and are located at distances between 9 and 47pc. They lie above and on the sequence of field dwarfs in the diagrams of absolute J and Ks magnitude versus spectral type and luminosity versus effective temperature, which implies ages similar to or smaller than those typical of the field. In the HR diagram, 2MASS J00332386-1521309 (L4), 2MASSJ00452143+1634446 (L2), 2MASSJ03552337+1133437 (L5), 2MASSJ05012406-0010452 (L4), G196-3B (L3), 2MASSJ17260007+1538190 (L3), and 2MASSJ22081363+2921215 (L3) occupy locations that are compatible with the most likely ages in the interval ≃10-500Myr if they are single objects. All of these dwarfs (except for 2MASSJ00332386-1521309) show strong lithium absorption at 670.8 nm, thus confirming the young ages and masses ranging from ≃11 through ≃45MJup for this subsample. The detection of atomic lithium in the atmosphere of 2MASSJ00452143+1634446 (L2) is reported for the first time. The lack of lithium in 2MASSJ00332386-1521309 (L4) is not compatible with its position in the HR diagram, suggesting a spectral type earlier than L4. The remaining three dwarfs, 2MASSJ02411151-0326587 (L0), 2MASSJ10224821+5825453 (L1), and 2MASSJ15525906+2948485 (L0) have locations in the HR diagram indicative of older ages and higher masses consistent with the observed lithium depletion previously published. The dynamical studies based on space velocities derived from our parallaxes and proper motions fully support the aforementioned results for 2MASSJ00452143+1634446, 2MASSJ03552337+1133437, G196-3B, 2MASSJ10224821+5825453, and 2MASSJ15525906+2948485. We did not find evidence for the presence of astrometric companions with minimum detectable masses that are typically ≥25MJup and face-on, circular orbits with periods between 60-90 d and 3 yr around eight targets. The astrometric and spectroscopic data indicate that about 60-70% of the field L-type dwarfs in our sample with evidence for low-gravity atmospheres are indeed young-to-intermediate-age brown dwarfs of the solar neighborhood with expected ages and masses in the intervals ≃10-500Myr and ≃11-45MJup. The peaked-shape of the H-band spectra of L dwarfs, a signpost of youth, appears to be present up to ages of 120-500Myr and intermediate-to-high gravities.

Abstract Copyright:

Journal keyword(s): brown dwarfs - stars: low-mass - stars: distances - astrometry - proper motions

Simbad objects: 29

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Number of rows : 29

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 NAME THA As* 00 00 -62.0           ~ 317 0
2 2MASS J00332386-1521309 BD* 00 33 23.8720639269 -15 21 30.866646406           L4 20 0
3 EGGR 382 WD? 00 33 54.4629052338 -12 07 58.777597136 15.511 15.572 14.891 14.467 14.051 DC? 89 0
4 2MASS J00452143+1634446 BD* 00 45 21.4154136422 +16 34 44.738533078           L0beta 44 0
5 2MASS J00470038+6803543 BD* 00 47 00.387 +68 03 54.37           L9pec 50 0
6 2MASS J02411151-0326587 BD* 02 41 11.52 -03 26 58.8           L0 25 0
7 Cl Melotte 20 OpC 03 26 42 +48 48.0           ~ 741 0
8 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 2908 0
9 2MASS J03552337+1133437 BD* 03 55 23.3772215371 +11 33 43.796763263           L3-L6 81 0
10 NAME NGC 1566 Group GrG 04 20 00.6 -54 56 17           ~ 125 0
11 NAME Taurus Dark Cloud SFR 04 41.0 +25 52           ~ 3309 0
12 2MASS J05012406-0010452 BD* 05 01 24.0863586627 -00 10 45.584828608           L4 36 0
13 Cl Collinder 65 Cl* 05 26 06 +16 42.0           ~ 27 0
14 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 472 0
15 IC 2391 OpC 08 40 32 -53 02.0           ~ 703 0
16 G 196-3B BD* 10 04 20.6389184345 +50 22 59.448807780           L2 89 0
17 G 196-3 Ro* 10 04 21.4628959388 +50 23 13.387216700       11.323   M3.0V 69 0
18 2MASS J10224821+5825453 BD* 10 22 48.2222984613 +58 25 45.394831331           L0.6V 32 0
19 IC 2602 OpC 10 42 58 -64 24.0           ~ 538 0
20 NAME beta Pic Moving Group MGr 14 30 -42.0           ~ 524 0
21 2MASS J15525906+2948485 BD* 15 52 59.0621662551 +29 48 48.576310914           L0e 26 0
22 2MASSI J1726000+153819 BD* 17 26 00.08 +15 38 19.0           L2V 37 1
23 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11007 0
24 2MASS J21140802-2251358 BD* 21 14 08.026 -22 51 35.84           L7+1 66 0
25 * eps Ind B BD* 22 04 10.52 -56 46 57.7     24.12 20.8 15.60 T1V+T6V 121 2
26 2MASSW J2208136+292121 BD* 22 08 13.63 +29 21 21.5           L2Vpec 43 0
27 NAME Pleiades Moving Group MGr ~ ~           ~ 227 1
28 NAME AB Dor Moving Group MGr ~ ~           ~ 332 0
29 NAME Argus Association As* ~ ~           ~ 155 0

    Equat.    Gal    SGal    Ecl

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2019.10.22-11:57:46

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