High Resolution Imaging of Very Low Mass Spectral Binaries: Three Resolved Systems and Detection of Orbital Motion in an L/T Transition Binary
We present high resolution Laser Guide Star Adaptive Optics imaging of 43 late-M, L and T dwarf systems with Keck/NIRC2. These include 17 spectral binary candidates, systems whose spectra suggest the presence of a T dwarf secondary. We resolve three systems: 2MASS J1341–3052, SDSS J1511+0607 and SDSS J2052–1609; the first two are resolved for the first time. All three have projected separations <8 AU and estimated periods of 14–80 years. We also report a preliminary orbit determination for SDSS J2052–1609 based on six epochs of resolved astrometry between 2005 and 2010. Among the 14 unresolved spectral binaries, 5 systems were confirmed binaries but remained unresolved, implying a minimum binary fraction of 47_(-11)^(+12) for this sample. Our inability to resolve most of the spectral binaries, including the confirmed binaries, supports the hypothesis that a large fraction of very low mass systems have relatively small separations and are missed with direct imaging.
© 2015. The American Astronomical Society. Received 2015 August 31; accepted 2015 September 29; published 2015 November 2. We would like to thank our referee, Sandy Leggett, for her helpful comments. The authors thank observing assistants Jason McIlroy, Heather Hershley, Terry Stickel, and Gary Puniwai and support astronomers Hien Tran, Luca Rizzi, Marc Kassis, and Al Conrad for their assistance during our observations. D. B. G. acknowledges funding support from the IPAC graduate fellowship. D. B. G. and A. J. B. acknowledge support from the National Aeronautics and Space Administration under Grant No. NNX15AI75G. C. R. G. was partially supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This publication makes use of data from the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at http://www.browndwarfs.org/spexprism; the Dwarf Archives Compendium, maintained by Chris Gelino, Davy Kirkpatrick, Mike Cushing, David Kinder and Adam Burgasser at http://DwarfArchives.org; and the VLM Binaries Archive maintained by Nick Siegler at http://vlmbinaries.org. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck NIRC2 - .
Published - Gagliuffi_2015p163.pdf
Submitted - 1510.00392v1.pdf