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Published December 2015 | Published + Submitted
Journal Article Open

Radio Emission and Orbital Motion from the Close-encounter Star–Brown Dwarf Binary WISE J072003.20–084651.2


We report the detection of radio emission and orbital motion from the nearby star–brown dwarf binary WISE J072003.20–084651.2AB. Radio observations across the 4.5–6.5 GHz band with the Very Large Array identify at the position of the system quiescent emission with a flux density of 15 ± 3 μJy, and a highly polarized radio source that underwent a 2–3 minute burst with peak flux density 300 ± 90 μJy. The latter emission is likely a low-level magnetic flare similar to optical flares previously observed for this source. No outbursts were detected in separate narrow-band Hα monitoring observations. We report new high-resolution imaging and spectroscopic observations that confirm the presence of a co-moving T5.5 secondary and provide the first indications of three-dimensional orbital motion. We used these data to revise our estimates for the orbital period (4.1_(-1.3)^(+2.7) year) and tightly constrain the orbital inclination to be nearly edge-on (93º6^(+1º6)_(−1º4)), although robust measures of the component and system masses will require further monitoring. The inferred orbital motion does not change the high likelihood that this radio-emitting very low-mass binary made a close pass to the Sun in the past 100 kyr.

Additional Information

© 2015. The American Astronomical Society. Received 2015 July 10; accepted 2015 August 24; published 2015 November 18. The authors thank Randy Campbell, Heather Hershley, and Marc Kassis at Keck Observatory; and Pavl Zachary and Shawn Stone at Lick Observatory for their assistance with the observations. We thank our anonymous referee for her/his/their helpful comments, particularly on the MCMC analysis. C. M. acknowledges funding support from the National Science Foundation under award No. AST-1313428. The material is based upon work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France; NASA's Astrophysics Data System Bibliographic Services; the M, L, T, and Y dwarf compendium housed at DwarfArchives.org; and the SpeX Prism Libraries at http://www.browndwarfs.org/spexprism. Research at Lick Observatory is partially supported by a generous gift from Google. The authors 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 and grateful to have the opportunity to conduct observations from this mountain.

Attached Files

Published - Burgasser_2015p180.pdf

Submitted - 1508.06332v1.pdf


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August 22, 2023
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