The Young L Dwarf 2MASS J11193254−1137466 Is a Planetary-mass Binary

Journal Article · Sat Jul 01 04:00:00 EDT 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA76DF· OSTI ID:22872611

Best, William M. J.; Liu, Michael C.; Magnier, Eugene A. ^[1]

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1. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

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{sub −0.9}{sup +1.2} M{sub Jup} brown dwarfs, making it the lowest-mass binary discovered to date. We estimate an orbital period of 90{sub −50}{sup +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 T{sub eff} 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.

• OSTI ID: 22872611
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 843; ISSN 2041-8205
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BENCHMARKS
DISTANCE
GRAVITATION
IMAGES
INFRARED SPECTRA
LASERS
OPTICS
PHOTOMETRY
PROBABILITY
PROPER MOTION
STARS