Discovery of a Nearby Star-Brown Dwarf Binary

The nearest star systems to the Sun are some of the most heavily studied, as their proximity makes them brighter and easier to observe. Moreover, nearby systems can be studied at finer resolution than distant ones, making it easier to detect astrometric motion (parallax, proper motion, orbital motion), close companions, and even circumstellar structures such as disks and jets.  As astronomers probe ever cooler stars and brown dwarfs, we are constantly finding new neighbors, such as the recently discovered L dwarf + T dwarf binary Luhman 16AB (3rd closest to the Sun) and the frigid Y dwarf WISE J0855-0714, both around 2 pc (6 lightyears) away.

One of the recent nearby star discoveries is WISE J0720-0846 (Figure 1), uncovered by Ralf-Dieter Scholz in a cross-match of the WISE and 2MASS surveys.  At ~7 pc, this apparently cool late M or L dwarf is an exciting new addition to the Solar Neighborhood. So of course we had to get a peek at it.

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Cloud properties of Nearest Brown Dwarfs Revealed through Spectral Monitoring Study

starweatherWe’ve just reported the first results from our April 2013  campaign to monitor the nearby brown dwarf binary Luhman 16AB, in a paper published in the Astrophysical Journal.  Our results confirm the earlier “flux reversal” seen in FIRE spectroscopy, and allow us to make the first constraints on the cloud coverage fraction and the temperatures of the “clouds” and “holes” in the atmosphere of Luhman 16B.  We also confirm an apparent correlation between rotation period and variability amplitude, which may emerge if cloud features are related to the Rhine’s scale of brown dwarf atmospheres.

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Worldwide Campaign for Luhman 16AB

This week, members of the Cool Star Lab and colleagues in the US, Europe, Chile, and South Africa will be targeting the newly-discovered nearby brown dwarf binary Luhman 16AB (aka WISE 1049-5319).  This very exciting source has been shown to be variable on timescales of hours thanks to data acquired with the TRAPPIST telescope. We’ll be extending this work with photometric and spectroscopic observations in the optical and near-infrared from La Silla Observatory, Cerro Tololo ObservatoryLas Campanas du Pont Observatory, Magellan Telescopes, Keck Observatory, the NASA Infrared Telescope Facility and the South African Large Telescope.  We’ll also be attempting high resolution spectroscopic observations to measure rotational and orbital motions.  Stay tuned!

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Observations of Luhman 16AB: A Brown Dwarf Binary at 2 pc

Early in March 2013, Kevin Luhman announced his discovery of a pair of brown dwarfs only 2 pc (6 light-years) from the Sun, the 3rd closest system to us after the α/Proxima Centauri system and Barnard’s Star. This remarkable find was buried in survey data going back 35 years, but elucidated with the mid-infrared sensitivity of the Wide-field Infrared Survey Explorer (WISE) and the object’s very high proper motion (2.8 arcseconds/year, or just under 0.1 degrees/century).  Using optical spectroscopy, Luhman found that the brighter of the two components had a late-L spectral type, suggesting that the system might straddle the transition between L dwarf and T dwarf spectral classes.  Knowing home much we like this really cool transition, we jumped into action.

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