New objects closer than 10 parsecs

http://arxiv.org/abs/1006.3577

Quote :

DENIS J081730.0-615520: An overlooked mid-T dwarf in the solar neighborhood
Étienne Artigau, Jacqueline Radigan, Stuart Folkes, Ray Jayawardhana, Radostin Kurtev, David Lafrenière, René Doyon, Jura Borissova
(Submitted on 17 Jun 2010)
Recent wide-field near-infrared surveys have uncovered a large number of cool brown dwarfs, extending the temperature sequence down to less than 500 K and constraining the faint end of the luminosity function. One interesting implication of the derived luminosity function is that the brown dwarf census in the immediate (<10 pc) solar neighborhood is still largely incomplete, and some bright (J<16) brown dwarfs remain to be identified in existing surveys. These objects are especially interesting as they are the ones that can be studied in most detail, especially with techniques that require large fluxes (e.g. time-variability, polarimetry, high-resolution spectroscopy) that cannot realistically be applied to objects uncovered by deep surveys. By cross-matching the DENIS and the 2MASS point-source catalogs, we have identified an overlooked brown dwarf -DENIS J081730.0-615520- that is the brightest field mid-T dwarf in the sky (J = 13.6). We present astrometry and spectroscopy follow-up observations of this brown dwarf. Our data indicate a spectral type T6 and a distance -from parallax measurement- of 4.9\pm0.3 pc, placing this mid-T dwarf among the 3 closest isolated brown dwarfs to the Sun.

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The measured distance for DENIS0817 is 4.9 ± 0.3 pc, making it one of the closest BDs to the Sun, and only second (or third, given the uncertainty) among isolated BDs, the closest previously known being UGPS J0722-05 (T9+, 2.9 ± 0.4 pc, Lucas et al. 2010) and DENIS-P J0255-4700, (L8, 5.0 ± 0.1 pc, Mart´ın et al. 1999; Costa et al. 2006). There are also 3 T dwarfs in orbit around nearby stars within 5 pc:  Indi Bab (T1/T6, 3.63±0.01 pc, Scholz et al. 2003) and SCR 1845-6357B (T6, 3.85 ± 0.02 pc, Biller et al. 2006).

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In retrospect, DENIS0817 was overlooked by previous searches in the DENIS and
2MASS surveys due to its relative proximity (l = −14, b = 276) to the galactic plane
even though it is in a field sparse enough to allow for an efficient BD search without the
crowding issues normally associated with moving object searches in the galactic plane.

http://www.jpl.nasa.gov/news/news.cfm?release=2010-210

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Astronomers have uncovered what appear to be 14 of the coldest stars known in our universe. These failed stars, called brown dwarfs, are so cold and faint that they'd be impossible to see with current visible-light telescopes. Spitzer's infrared vision was able to pick out their feeble glow, much as a firefighter uses infrared goggles to find hot spots buried underneath a dark forest floor.

The brown dwarfs join only a handful of similar objects previously discovered. The new objects are between the temperatures of about 450 Kelvin to 600 Kelvin (350 to 620 degrees Fahrenheit). As far as stars go, this is bitter cold -- as cold, in some cases, as planets around other stars.

But apparently they are talking about this discovery
http://arxiv.org/abs/1004.1436
Therefore, these 14 BD are more farther to 10 parsecs.

http://wise.ssl.berkeley.edu/gallery_firstBD.html

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This particular object, named "WISEPC J045853.90+643451.9" after its location in the sky, is the first ultra-cool brown dwarf discovered by NASA's Wide-field Infrared Survey Explorer, or WISE. WISE is scanning the skies in infrared light, picking up the signatures of all sort of cosmic gems, including brown dwarfs.

The brown dwarf is located 18 to 30 light-years away in the northern constellation of Camelopardalis, or the giraffe; in fact, the brown dwarf is positioned right on the neck of the giraffe, adorning it like an emerald necklace. This is one of the coolest brown dwarfs known, with a temperature of roughly 600 Kelvin, or 620 degrees Fahrenheit.