Resolving the L/T transition binary SDSS J2052-1609 AB

Abstract

Binaries provide empirical key constraints for star formation theories, like the overall binary fraction, mass ratio distribution and the separation distribution. They play a crucial role to calibrate the output of theoretical models, like absolute magnitudes, colors and effective temperature depending on mass, metallicity and age. We present first results of our on-going high-resolution imaging survey of late type brown dwarfs. The survey aims at resolving tight brown dwarf binary systems to better constrain the T dwarf binary fraction. We intent to follow-up the individual binaries to determine orbital parameters. Using NACO at the VLT we performed AO-assisted near-infrared observations of SDSS J2052-1609. High-spatial resolution images of the T1 dwarf were obtained in H and Ks filters. We resolved SDSS J2052-1609 into a binary system with a separation of 0.101" \pm 0.001". Archival data from HST/NICMOS taken one year previous to our observations proves the components to be co-moving. Using the flux ratio between the components we infer J, H and Ks magnitudes for the resolved system. From the near-IR colors we estimate spectral types of T1 +1 -4 and T2.5 \pm 1 for component A and B, respectively. A first estimate of the total system mass yields Mtot > 78 Mjup, assuming a circular orbit.

5 pages, 3 figures, 3 tables, accepted for publication by A&A

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• Weather on Other Worlds. II. Survey Results: Spots Are Ubiquitous on L and T Dwarfs
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• Individual Dynamical Masses of Ultracool Dwarfs
• SpeX Spectroscopy of Unresolved Very Low Mass Binaries. II. Identification of Fourteen Candidate Binaries with Late-M/Early-L and T Dwarf Components
• Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3$\pi$ Survey
• The Brown dwarf Atmosphere Monitoring (BAM) Project I: The largest near-IR monitoring survey of L- & T-dwarfs
• High Resolution Imaging of Very Low Mass Spectral Binaries: Three Resolved Systems and Detection of Orbital Motion in an L/T Transition Binary
• Constraints on the binary Properties of mid to late T dwarfs from Hubble Space Telescope WFC3 Observations