Astrophys. J., 843, L4-L4 (2017/July-1)
The young L dwarf 2MASS J11193254-1137466 is a planetary-mass binary.
BEST W.M.J., LIU M.C., DUPUY T.J. and MAGNIER E.A.
Abstract (from CDS):
We have discovered that the extremely red, low-gravity L7 dwarf 2MASS J11193254-1137466 is a 0.''14 (3.6 au) binary using Keck laser guide star adaptive optics imaging. 2MASS J11193254-1137466 has previously been identified as a likely member of the TW Hydrae Association (TWA). Using our updated photometric distance and proper motion, a kinematic analysis based on the BANYAN II model gives an 82% probability of TWA membership. At TWA's 10 ± 3 Myr age and using hot-start evolutionary models, 2MASS J11193254-1137466AB is a pair of 3.7–0.9+1.2MJup brown dwarfs, making it the lowest-mass binary discovered to date. We estimate an orbital period of 90–50+80 years. One component is marginally brighter in K band but fainter in J band, making this a probable flux-reversal binary, the first discovered with such a young age. We also imaged the spectrally similar TWA L7 dwarf WISEA J114724.10-204021.3 with Keck and found no sign of binarity. Our evolutionary model-derived Teff estimate for WISEA J114724.10-204021.3 is ≃230 K higher than for 2MASS J11193254-1137466AB, at odds with the spectral similarity of the two objects. This discrepancy suggests that WISEA J114724.10-204021.3 may actually be a tight binary with masses and temperatures very similar to 2MASS J11193254-1137466AB, or further supporting the idea that near-infrared spectra of young ultracool dwarfs are shaped by factors other than temperature and gravity. 2MASS J11193254-1137466AB will be an essential benchmark for testing evolutionary and atmospheric models in the young planetary-mass regime.
© 2017. The American Astronomical Society. All rights reserved.
binaries: close - brown dwarfs - stars: individual: (2MASS J11193254-1137466, WISEA J114724.10-204021.3) - stars: individual: (2MASS J11193254-1137466, WISEA J114724.10-204021.3)
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