On the kinematic age of brown dwarfs: radial velocities and space motions of 43 nearby L dwarfs

Seifahrt, Andreas; Reiners, A.; Almaghrbi, Khiria A. M.; Basri, Gibor

doi:10.1051/0004-6361/200913368

Cited by 47 publications

(78 citation statements)

References 41 publications

(84 reference statements)

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“…This procedure was checked using archival UVES spectra for the L1 dwarf 2MASS J10484281+0111580 from ESO program ID 078.C-0025(A) (PI A. Reiners). With our method we obtained a heliocentric radial velocity of 21.9 ± 1.4 km s −1 , which is consistent with the published value of 24.0 ± 1.1 km s −1 (Seifahrt et al 2010). No significant (i.e.…”

Section: Radial Velocity Measurementssupporting

confidence: 91%

“…This measurement will be discussed in Burgasser et al (in prep.). Using 32 sources that were both observed with MagE and with UVES (Seifahrt et al 2010;Reiners & Basri 2009), we determined an average velocity offset between both instruments and reduction methods of −0.29 ± 0.59 km s −1 . It is small and not significant, especially when compared to the uncertainty of the MagE measurement of DE0823−49, and we therefore neglected it in our analysis.…”

Section: Radial Velocity Measurementsmentioning

confidence: 99%

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DE0823−49 is a juvenile binary brown dwarf at 20.7 pc

Burgasser

Martín

Lazorenko

et al. 2015

A&A

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Astrometric monitoring of the nearby early-L dwarf DE0823−49 has revealed a low-mass companion in a 248-day orbit that was announced in an earlier work. Here, we present new astrometric and spectroscopic observations that allow us to characterise the system in detail. The optical spectrum shows Li -absorption indicative of a young age and/or substellar mass for the primary component.The near-infrared spectrum is best reproduced by a binary system of brown dwarfs with spectral types of L1.5 + L5.5 and effective temperatures of 2150 ± 100 K and 1670 ± 140 K. To conform with the photocentric orbit size measured with astrometry and the current understanding of substellar evolution, the system must have an age in the 80−500 Myr range. Evolutionary models predict component masses in the ranges of M 1 0.028−0.063 M and M 2 0.018−0.045 M with a mass ratio of q 0.64−0.74. Multiepoch radial velocity measurements unambiguously establish the three-dimensional orbit of the system and allow us to investigate its kinematic properties. DE0823−49 emerges as a rare example of a nearby brown dwarf binary with orbit, component properties, and age that are characterised well. It is a juvenile resident of the solar neighbourhood, but does not appear to belong to a known young association or moving group.

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Section: Radial Velocity Measurementssupporting

confidence: 91%

Section: Radial Velocity Measurementsmentioning

confidence: 99%

DE0823−49 is a juvenile binary brown dwarf at 20.7 pc

Burgasser

Martín

Lazorenko

et al. 2015

A&A

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“…With the only exception of J1022+5825, the space velocities of the remaining L dwarfs are consistent with the Galaxy young disk kinematics, according to the classification made by Eggen (1990) and Leggett (1992). The UVW velocities of J1022+5825 reported here differ from those given by Seifahrt et al (2010), Blake et al (2010), and Allers & Liu (2013) because of our larger proper motion measurement (see Sect. 4.2).…”

Section: Space Velocitiessupporting

confidence: 83%

Trigonometric parallaxes of young field L dwarfs

Osorio

Béjar

Miles-Páez

et al. 2014

A&A

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Aims. 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 HertzsprungRussell (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. Methods. We obtained J and K s imaging data using 2-4 m 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, 500-1100 nm) using the 10 m 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 T eff , 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. Results. Trigonometric parallaxes and proper motions were derived to typical accuracies of a milliarcsecond (mas) and ±10 mas yr −1 , respectively. All ten L dwarfs have large motions (μ ≥ 70 mas yr −1 ) and are located at distances between 9 and 47 pc. They lie above and on the sequence of field dwarfs in the diagrams of absolute J and K s 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), 2MASS J00452143+1634446 (L2), 2MASS J03552337+1133437 (L5), 2MASS J05012406−0010452 (L4), G 196-3B (L3), 2MASS J17260007+1538190 (L3), and 2MASS J22081363+2921215 (L3) occupy locations that are compatible with the most likely ages in the interval ≈10-500 Myr if they are single objects. All of these dwarfs (except for 2MASS J00332386−1521309) show strong lithium absorption at 670.8 nm, thus confirming the young ages and masses ranging from ≈11 through ≈45 M Jup for this subsample. The detection of atomic lithium in the atmosphere of 2MASS J00452143+1634446 (L2) is reported for the first time. The lack of lithium in 2MASS J00332386−1521309 (L4) is not compatible with its position in the HR diagram, suggesting a spectral type earlier than L4. The remaining three dwarfs, 2MASS J02411151−0326587 (L0), 2MASS J10224821+5825453 (L1), and 2MASS J15525906+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 2MASS J00452143+1634446, 2MASS J03552337+1133437, G 196-3B, 2MASS J10224821+5825453, and 2MASS J15525906+2948485. We did ...

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“…Our remaining objects were flagged by Seifahrt et al (2010) as candidates of the nearby moving groups studied by Montes et al (2001): the Pleiades (1 object; 130±20 Myr [Barrado y Navascués et al 2004]), Ursa Majoris (2 objects; ≈400-500 Myr Jones et al 2015]), and Hyades (4 objects; ≈600-800 Myr) moving groups. Note that these are not the open clusters themselves, but rather more dispersed stars claimed to be coeval with the clusters.…”

Section: Samplementioning

confidence: 99%

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

Liu

Dupuy

Allers

2016

ApJ

236

320

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We present a large, uniform analysis of young (≈10-150 Myr) ultracool dwarfs, based on new high-precision infrared (IR) parallaxes for 68 objects. We find that low-gravity (vl-g) late-M and L dwarfs form a continuous sequence in IR color-magnitude diagrams, separate from the field population and from current theoretical models. These vl-g objects also appear distinct from young substellar (brown dwarf and exoplanet) companions, suggesting the two populations may have a different range of physical properties. In contrast, at the L/T transition, young, old, and spectrally peculiar objects all span a relatively narrow range in near-IR absolute magnitudes. At a given spectral type, the IR absolute magnitudes of young objects can be offset from ordinary field dwarfs, with the largest offsets occurring in the Y and J bands for late-M dwarfs (brighter than the field) and mid/late-L dwarfs (fainter than the field). Overall, low-gravity (vl-g) objects have the most uniform photometric behavior while intermediate-gravity (int-g) objects are more diverse, suggesting a third governing parameter beyond spectral type 1 This work is largely based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, and the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.2 Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. -2 -and gravity class. We examine the moving group membership for all young ultracool dwarfs with parallaxes, changing the status of 23 objects (including 8 previously identified planetary-mass candidates) and fortifying the status of another 28 objects. We use our resulting age-calibrated sample to establish empirical young isochrones and show a declining frequency of vl-g objects relative to int-g objects with increasing age. Notable individual objects in our sample include high-velocity ( 100 km s −1 ) int-g objects; very red late-L dwarfs with high surface gravities; candidate disk-bearing members of the MBM20 cloud and β Pic moving group; and very young distant interlopers. Finally, we provide a comprehensive summary of the absolute magnitudes and spectral classifications of young ultracool dwarfs, using a combined sample of 102 objects found in the field and as substellar companions to young stars.Subject headings: brown dwarfs -proper motions -parallaxes -solar neighborhood IntroductionObservational studies of brown dwarfs have been inspired by two complementary perspectives. One has been the desire to expand the parameter space of classical stellar astrophysics. Brown dwarfs are t...

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On the kinematic age of brown dwarfs: radial velocities and space motions of 43 nearby L dwarfs

Cited by 47 publications

References 41 publications

DE0823−49 is a juvenile binary brown dwarf at 20.7 pc

DE0823−49 is a juvenile binary brown dwarf at 20.7 pc

Trigonometric parallaxes of young field L dwarfs

The Hawaii Infrared Parallax Program. Ii. Young Ultracool Field Dwarfs* †

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