The Oceanus Moving Group: A New 500 Myr-Old Host for the Nearest Brown Dwarf

Abstract

We report the discovery of the Oceanus moving group, a $\approx$ 500 Myr-old group with 50 members and candidate members at distances 2-50 pc from the Sun using an unsupervised clustering analysis of nearby stars with Gaia DR3 data. This new moving group includes the nearest brown dwarf WISE J104915.57-531906.1 AB (Luhman 16 AB) at a distance of 2 pc, which was previously suspected to be young (600-800 Myr) based on a comparison of its dynamical mass measurements with brown dwarf evolutionary models. We use empirical color-magnitude sequences, stellar activity and gyrochronology to determine that this new group is roughly coeval with the Coma Ber open cluster, with an isochronal age of 510 $\pm$ 95 Myr. This newly discovered group will be useful to refine the age and chemical composition of Luhman 16 AB, which is already one of the best substellar benchmarks known to date. Furthermore, the Oceanus moving group is one of the nearest young moving groups identified to date, making it a valuable laboratory for the study of exoplanets and substellar members, with 8 brown dwarf candidate members already identified here.

Accepted in ApJ. 32 pages, 6 figures, 6 tables

References in corpus (42)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Painting a portrait of the Galactic disc with its stellar clusters
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• A catalogue of white dwarfs in Gaia EDR3
• The Gemini Deep Planet Survey -- GDPS
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• The CatWISE2020 Catalog
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
• Constraining the thick disc formation scenario of the Milky Way
• A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups
• BANYAN. V. A Systematic All-Sky Survey for New Very Late-Type Low-Mass Stars and Brown Dwarfs in Nearby Young Moving Groups
• Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories
• A Volume-Limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
• Variability Properties of 4 Million Sources in the $TESS$ Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey
• Discovery of Tidal Tails in Disrupting Open Clusters: Coma Berenices and a Neighbor Stellar Group
• BANYAN. IX. The Initial Mass Function and Planetary-Mass Object Space Density of the TW Hya Association
• Praesepe (NGC 2632) and its tidal tails
• The Hawaii Infrared Parallax Program. IV. A Comprehensive Parallax Survey of L0-T8 dwarfs with UKIRT
• Spitzer Variability Properties of Low-Gravity L Dwarfs
• Signatures of Cloud, Temperature, and Gravity From Spectra of the Closest Brown Dwarfs
• A Number of Nearby Moving Groups may be Fragments of Dissolving Open Clusters
• Photometric brown-dwarf classification. I. A method to identify and accurately classify large samples of brown dwarfs without spectroscopy
• Accurate age determinations of several nearby open clusters containing magnetic Ap stars
• The CARMENES search for exoplanets around M dwarfs. Mapping stellar activity indicators across the M dwarf domain
• The CARMENES search for exoplanets around M dwarfs: Convective shift and starspot constraints from chromatic radial velocities
• The unpopular Package: a Data-driven Approach to De-trend TESS Full Frame Image Light Curves
• Lithium depletion boundary, stellar associations, and Gaia
• wdwarfdate: A Python Package to Derive Bayesian Ages of White Dwarfs
• New Coronae and Stellar Associations Revealed by a Clustering Analysis of the Solar Neighborhood
• Gyrochronological dating of the stellar moving group Group X
• Extended Tidal Tails of IC 4756 detected by {\it Gaia} EDR3
• Individual, Model-Independent Masses of the Closest Known Brown Dwarf Binary to the Sun
• Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit
• The old moving groups in the field of Taurus

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• A review of unsupervised learning in astronomy
• The JWST Weather Report from the Nearest Brown Dwarfs I: multi-period JWST NIRSpec + MIRI monitoring of the benchmark binary brown dwarf WISE 1049AB
• The ESO SupJup Survey VII: Clouds and line asymmetries in CRIRES${}^{+}$ J-band spectra of the Luhman 16 binary
• The ESO SupJup Survey VIII. Chemical fingerprints of young L dwarf twins
• HST astrometry of the closest Brown Dwarfs -- II. Improved parameters and constraints on a third body
• A study of the frequency and characteristics of stellar companions and Jupiter-like planets in nearby open clusters
• Sensitivity to Sub-Io-sized Exosatellite Transits in the MIRI LRS Lightcurve of the Nearest Substellar Worlds