University of Hertfordshire

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From the same journal

2MASS 0213+3648 C: A wide T3 benchmark companion to an an active, old M dwarf binary

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  • N. R. Deacon
  • E. A. Magnier
  • Michael C. Liu
  • Joshua E. Schlieder
  • Kimberly M. Aller
  • William M. J. Best
  • Brendan P. Bowler
  • W. S. Burgett
  • K. C. Chambers
  • P. W. Draper
  • H. Flewelling
  • K. W. Hodapp
  • N. Kaiser
  • N. Metcalfe
  • W. E. Sweeney
  • R. J. Wainscoat
  • C. Waters
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Original languageEnglish
Pages (from-to)1126-1139
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Early online date24 Jan 2017
Publication statusPublished - 1 May 2017


We present the discovery of a 360 AU separation T3 companion to the tight (3.1 AU) M4.5+M6.5 binary 2MASS J02132062+3648506. This companion was identified using Pan-STARRS1 data and, despite its relative proximity to the Sun (22.2$_{-4.0}^{+6.4}$ pc; Pan-STARRS1 parallax) and brightness ($J$=15.3), appears to have been missed by previous studies due to its position near a diffraction spike in 2MASS. The close M~dwarf binary has active X-ray and H$\alpha$ emission and shows evidence for UV flares. The binary's weak {\it GALEX} UV emission and strong Na I 8200\AA Na absorption leads us to an age range of $\sim$1-10Gyr. Applying this age range to evolutionary models implies the wide companion has a mass of 0.063$\pm$0.009\,$M_{\odot}$. 2MASS J0213+3648 C provides a relatively old benchmark close to the L/T transition and acts as a key, older comparison to the much younger early-T companions HN~Peg~B and GU~Psc~b.


This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2017 The Author (s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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