Luhman 16 (WISE J104915.57-531906.1) : Nearest BD System

Luhman 16 = WISE J104915.57-531906.1

Possible astrometric discovery of a substellar companion to the closest binary brown dwarf system WISE J104915.57-531906.1

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Using FORS2 on the Very Large Telescope, we have astrometrically monitored over a period of two months the two components of the brown dwarf system WISE J104915.57-531906.1, the closest one to the Sun. Our astrometric measurements - with a relative precision at the milli-arcsecond scale - allow us to detect the orbital motion and derive more precisely the parallax of the system, leading to a distance of 2.020+/-0.019 pc. The relative orbital motion of the two objects is found to be perturbed, which leads us to suspect the presence of a substellar companion around one of the two components. We also perform VRIz photometry of both components and compare with models. We confirm the flux reversal of the T dwarf.

ESO VLT Doppler mapping of the secondary.
http://www.eso.org/public/news/eso1404/

Do we not have a thread for this object already?

Sahlmann & Lazorenko "Mass ratio of the 2 pc binary brown dwarf LUH16 and limits on planetary companions from astrometry"
http://arxiv.org/abs/1506.07994

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We thus excluded that either of the LUH16 components harbours a giant planet more massive than twice the mass of Jupiter in a short period (20–300 d) orbit, which disagrees with the conclusions of Boffin et al. (2014). So far, the system appears to consist of only two components.

Maps of Evolving Cloud Structures in Luhman 16AB from HST Time-Resolved Spectroscopy
http://arxiv.org/abs/1605.01682

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WISE J104915.57-531906.1 is the nearest brown dwarf binary to our Solar system, consisting of two brown dwarfs in the L/T transition: Luhman 16A & B. In this paper we present the first map of Luhman 16A, and maps of Luhman 16B for two epochs. Our maps were created by applying Aeolus, a Markov-Chain Monte Carlo code that maps the top-of-the-atmosphere structure of brown dwarf and other ultracool atmospheres, to light curves of Luhman 16A & B using the Hubble Space Telescope's G141 and G102 grisms. Aeolus retrieved three or four spots in the top-of-the-atmosphere of Luhman 16A & B, with a surface coverage of 19%-32% (depending on an assumed rotational period of 5 hr or 8 hr) or 21%-38.5% (depending on the observational epoch) respectively. The brightness temperature of the spots of the best-fit models was ~200 K hotter than the background top-of-the-atmosphere. We compared our Luhman 16B map with the only previously published map. Interestingly, our map contained a large, cooler (DT~51 K) than the background top-of-the-atmosphere spot that lay at low latitudes, in agreement with the previous Luhman 16B map. Finally, we report the detection of a feature reappearing in Luhman 16B light curves that are separated by tens of hundreds of rotations from each other. We speculate this feature is related to top-of-the-atmosphere structures of Luhman 16B.

Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit
https://arxiv.org/abs/1706.00657

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Located at ~2pc, the L7.5+T0.5 dwarfs system WISE J104915.57-531906.1 (Luhman16AB) is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity, and planet-hosting frequency. In the first study of this series -- based on a multi-cycle Hubble Space Telescope (HST) program -- we provide an overview of the project and present improved estimates of positions, proper motions, annual parallax, mass ratio, and the current best assessment of the orbital parameters of the A-B pair. Our HST observations encompass the apparent periastron of the binary at 220.5+/-0.2 mas at epoch 2016.402. Although our data seem to be inconsistent with recent ground-based astrometric measurements, we also exclude the presence of third bodies down to Neptune masses and periods longer than a year.

The Neptune-sized third body hypothesis is not entirely discarded yet...

HST astrometry of the closest Brown Dwarfs -- II. Improved parameters and constraints on a third body

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Located at less than 2pc away, Luhman16AB (WISE.J104915.57-531906.1) is the closest pair of brown dwarfs and third closest `stellar' system to Earth. An exoplanet candidate in the Luhman16 binary system was reported in 2017 based on a weak astrometric signature in the analysis of 12 HST epochs. An additional epoch collected in 2018 and re-analysis of the data with more advanced methods further increased the significance level of the candidate, consistent with a Neptune-mass exoplanet orbiting one of the Luhman16 brown dwarf components. We report the joint analysis of these previous data together with two new astrometric HST epochs we obtained to confirm or disprove this astrometric signature. Our new analysis rules out presence of a planet orbiting one component of the Luhman16AB system for masses M > 1.5 M_Nep (Neptune masses) and periods between 400 and 5000 days. However, the presence of third bodies with masses M < 3 M_Nep and periods between 2 and 400 days (~1.1yrs) can not be excluded. Our measurements make significant improvements to the characterization of this sub-stellar binary, including its mass-ratio 0.8305+/-0.0006, individual component masses 35.4+/-0.2 M_Jup and 29.4+/-0.2 M_Jup (Jupiter masses), and parallax distance 1.9960pc +/- 50AU. Comparison of the masses and luminosities of Luhman16AB to several evolutionary models shows persistent discrepancies in the ages of the two components, but strengthens the case that this system is a member of the 510+/-95 Myr Oceanus Moving Group.