Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB

Abstract

We have resolved Kelu-1 into a binary system with a separation of ~290 mas using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We have also re-analyzed a 1998 HST observation of Kelu-1 and find that the observed PSF is best fit by a binary object separated by 45 mas. Observations on multiple epochs confirm the two objects share a common proper motion and clearly demonstrate the first evidence of orbital motion. Kelu-1B is fainter than Kelu-1A by 0.39+/-0.01 magnitudes in the K' filter and 0.50+/-0.01 magnitudes in the H filter. We derive spectral types of L2+/-1 and L3.5+/-1 for Kelu-1A and B, respectively. The separation of flux into the two components rectifies Kelu-1's over-luminosity problem that has been known for quite some time. Given the available data we are able to constrain the inclination of the system to >81 degrees and the orbital period to >~40 years.

arXiv comment15 pages, 3 figures, Accepted to PASP. Changes include: title, author list, new data, more analysis, and new journal

References in corpus (17)

• The USNO-B Catalog
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• Sixty-seven Additional L Dwarfs Discovered by the Two Micron All Sky Survey (2MASS)
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: the Effects of Temperature, Clouds, and Gravity
• L' and M' Photometry of Ultracool Dwarfs
• Preliminary Parallaxes of 40 L and T Dwarfs from the U.S. Naval Observatory Infrared Astrometry Program
• Infrared Spectra and Spectral Energy Distributions of Late-M- and L-Dwarfs
• An Effective Temperature Scale for Late M and L Dwarfs, from Resonance Absorption Lines of CsI and RbI
• JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems
• Dynamical Masses of the Binary Brown Dwarf GJ 569Bab
• Keck Imaging of Binary L Dwarfs
• Kelu-1 is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide Star Adaptive Optics
• Detection of Six Transneptunian Binaries with NICMOS: A High Fraction of Binaries in the Cold Classical Disk
• First determination of the dynamical mass of a binary L dwarf
• Periodic photometric variability of the brown dwarf Kelu-1
• Time resolved spectroscopy of the variable brown dwarf Kelu-1

Cited by in corpus (21)

• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field
• 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
• Binaries and the L Dwarf/T Dwarf Transition
• Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839-0446358
• Direct evidence of a sub-stellar companion around CT Cha
• Discovery of a T Dwarf Binary with the Largest Known J-Band Flux Reversal
• A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density
• The NIRSPEC Brown Dwarf Spectroscopic Survey II: High-Resolution J-Band Spectra of M, L and T Dwarfs
• A Cross-Match of 2MASS and SDSS. II. Peculiar L Dwarfs, Unresolved Binaries, and the Space Density of T Dwarf Secondaries
• A Chandra X-ray detection of the L dwarf binary Kelu-1: Simultaneous Chandra and Very Large Array observations
• Trigonometric Parallaxes and Proper Motions of 134 Southern Late M, L, and T Dwarfs from the Carnegie Astrometric Planet Search Program
• Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics
• Discovery of a Very Low Mass Triple with Late-M and T Dwarf Components: LP 704-48/SDSS J0006-0852AB
• 2MASS J20261584-2943124: An Unresolved L0.5 + T6 Spectral Binary
• Radial Velocity Variability of Field Brown Dwarfs
• Observations of Ultracool dwarfs with ULTRACAM on the VLT: a search for weather
• A Spitzer IRAC Imaging Survey for T Dwarf Companions Around M, L, and T Dwarfs: Observations, Results, and Monte Carlo Population Analyses
• The search for planetary mass companions to field brown dwarfs with HST/NICMOS
• SpeX Spectroscopy of Unresolved Very Low-Mass Binaries. I. Identification of Seventeen Candidate Binaries Straddling the L Dwarf/T Dwarf Transition