First determination of the dynamical mass of a binary L dwarf

Abstract

We present here the results of astrometric, photometric and spectroscopic observations leading to the determination of the orbit and dynamical masses of the binary L dwarf 2MASSW J0746425+2000321. High angular resolution observations spread over almost 4 years and obtained with the Hubble Space Telescope (HST), the ESO Very Large Telescope (VLT), and a the W. M. Keck Observatory (Keck) allow us to cover 36% of the period, corresponding to 60% of the orbit, and, for the first time, to derive a precise estimate of the total and individual masses of such a late-type object. We find an orbital period of 3850.9${}_{-767}^{+904}$ days. The corresponding total mass is 0.146${}_{-0.006}^{+0.016}$ M$_{\sun}$, with uncertainties depending on the distance. Spatially resolved low resolution optical (550--1025 nm) spectra have been obtained with HST/STIS, allowing us to measure the spectral types of the two components (L0$\pm$0.5 for the primary and L1.5$\pm$0.5 for the secondary). We also present precise photometry of the individual components measured on the high angular resolution images obtained with HST/ACS and WFPC2 (visible), VLT/NACO (J, H and Ks bands) and Keck I (Ks) band). These spectral and photometric measurements enable us to estimate their effective temperatures and mass ratio, and to place the object accurately in a H--R diagram. The binary system is most likely formed by a primary with a mass of 0.085$\pm$0.010 M$_{\sun}$ and a secondary with a mass of 0.066$\pm$0.006 M$_{\sun}$, thus clearly substellar, for an age of approximately 300$\pm$150 Myr. H$\alpha$ variability indicates chromospheric and/or magnetic activity.

accepted for publication in A&A 16 pages, 7 figures, 6 tables

References in corpus (19)

• The USNO-B Catalog
• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• Sixty-seven Additional L Dwarfs Discovered by the Two Micron All Sky Survey (2MASS)
• Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation
• Infrared Photometry of Late-M, L, and T Dwarfs
• Multiplicity of Nearby Free-floating Ultra-cool Dwarfs: a HST-WFPC2 search for companions
• An Effective Temperature Scale for Late M and L Dwarfs, from Resonance Absorption Lines of CsI and RbI
• A search for L dwarf binary systems
• Four nearby L dwarfs
• High resolution spectroscopy of ultracool M dwarfs
• L-dwarf variability: I-band observations
• The Multiplicity of the Hyades and its Implications for Binary Star Formation and Evolution
• The orbit of the brown dwarf binary Gl 569B
• Analysis of Keck HIRES spectra of early L-type dwarfs
• A mini-survey for variability in early L dwarfs
• Microarcsecond astrometry with Gaia: the solar system, the Galaxy and beyond

Cited by in corpus (59)

• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• BANYAN. VII. A New Population of Young Substellar Candidate Members of Nearby Moving Groups from the BASS Survey
• The AstraLux Large M-dwarf Multiplicity Survey
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• The NIRSPEC Ultracool Dwarf Radial Velocity Survey
• Individual Dynamical Masses of Ultracool Dwarfs
• Spitzer/IRAC Photometry of M, L, and T Dwarfs
• The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
• High Precision Dynamical Masses of Very Low Mass Binaries
• Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass Regime
• Periodic Radio and H-alpha Emission from the L Dwarf Binary 2MASSW J0746425+200032: Exploring the Magnetic Field Topology and Radius of an L Dwarf
• Keck Laser Guide Star Adaptive Optics Monitoring of 2MASS J1534-2952AB: First Dynamical Mass Determination of a Binary T Dwarf
• Discovery of a Highly Unequal-Mass Binary T Dwarf with Keck Laser Guide Star Adaptive Optics: A Coevality Test of Substellar Theoretical Models and Effective Temperatures
• Discovery of Two Very Low-Mass Binaries: Final Results of an Adaptive Optics Survey of Nearby M6.0-M7.5 Stars
• Kelu-1 is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide Star Adaptive Optics
• Two Extraordinary Substellar Binaries at the T/Y Transition and the Y-Band Fluxes of the Coolest Brown Dwarfs
• The Solar Neighborhood IX: Hubble Space Telescope Detections of Companions to Five M and L Dwarfs within 10 pc of the Sun
• The substellar mass function in sigma Orionis. II. Optical, near-infrared and IRAC/Spitzer photometry of young cluster brown dwarfs and planetary-mass objects
• A Panchromatic View of Brown Dwarf Aurorae
• The Monitor project: Searching for occultations in young open clusters
• CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System
• Astrometric orbit of a low-mass companion to an ultracool dwarf
• Optical Spectroscopic Classification and Membership of Young M Dwarfs in Star-Forming Regions
• Multiplicity of very low-mass objects in the Upper Scorpius OB association: a possible wide binary population
• Periodic Optical Variability of Radio Detected Ultracool Dwarfs
• A Spectroscopic Binary at the M/L Transition
• Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics
• Direct Detection of the Brown Dwarf GJ 802B with Adaptive Optics Masking Interferometry
• The Mass-Luminosity Relation in the L/T Transition: Individual Dynamical Masses for the New J-Band Flux Reversal Binary SDSSJ105213.51+442255.7AB
• Trigonometric Parallaxes for Two Late-Type Subdwarfs: LSR1425+71 (sdM8.0) and the Binary LSR1610-00 (sd?M6pec)
• LP 349-25: a new tight M8V binary
• A Mini-survey of Ultracool Dwarfs at 4.9 GHz
• A Search for L/T Transition Dwarfs With Pan-STARRS1 and WISE: Discovery of Seven Nearby Objects Including Two Candidate Spectroscopic Variables
• The GL 569 Multiple System
• Astrometric Discovery of GJ 802b: In the Brown Dwarf Oasis?
• Steady and Transient Radio Emission from Ultracool Dwarfs
• Spin-orbit alignment in the very low mass binary regime: The L dwarf tight binary 2MASSW J0746425+200032AB
• Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB
• On the dynamics of the ABDoradus system
• Resolved Hubble Space spectroscopy of ultracool binary systems
• Mid-Infrared Observations of the White Dwarf Brown Dwarf Binary GD 1400
• The Orbit of the L dwarf + T dwarf Spectral Binary SDSS J080531.84+481233.0
• Precise Dynamical Masses of Epsilon Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition
• Follow-up observations of binary ultra-cool dwarfs
• The ages of L dwarfs
• High contrast optical imaging of companions: the case of the brown dwarf binary HD-130948BC
• Improved radial velocity orbit of the young binary brown dwarf candidate ChaHa8
• Identification of partially resolved binaries in Pan-STARRS1 data
• High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM
• The Future of Ultracool Dwarf Science with JWST
• Multi-Epoch VLBI of L Dwarf Binary 2MASS J0746+2000AB: Precise Mass Measurements and Confirmation of Radio Emission from Both Components
• Resolving the L/T transition binary SDSS J2052-1609 AB
• The prospects for finding brown dwarfs in eclipsing binary systems and measuring brown dwarf properties
• Time-Resolved High Spectral Resolution Observation of 2MASSW J0746425+200032AB
• Local effects in astrometric binary orbits: perspective transformation and light-travel time
• The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey
• Low Mass Companions to White Dwarfs
• Detection and characterisation of two VLM binaries: LP 1033-31 and LP 877-72