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Post Info TOPIC: UGPSJ0722-05


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RE: UGPSJ0722-05
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Title: The Properties of the 500 K Dwarf UGPS J072227.51-054031.2, and a Study of the Far-Red Flux of Cold Brown Dwarfs
Authors: S. K. Leggett, D. Saumon, M. S. Marley, K. Lodders, J. Canty, P. Lucas, R. L. Smart, C. G. Tinney, D. Homeier, F. Allard, Ben Burningham, A. Day-Jones, B. Fegley, Miki Ishii, H. R. A. Jones, F. Marocco, D. J. Pinfield, M. Tamura

We present i and z photometry for 25 T dwarfs and one L dwarf. Combined with published photometry, the data show that the i - z, z - Y and z - J colours of T dwarfs are very red, and continue to increase through to the late-type T dwarfs, with a hint of a saturation for the latest types with T_eff ~ 600 K. We present new 0.7-1.0 um and 2.8-4.2 um spectra for the very late-type T dwarf UGPS J072227.51-054031.2, as well as improved astrometry for this dwarf. Examination of the spectral energy distribution using the new and published data, with Saumon & Marley models, shows that the dwarf has T_eff = 505 10 K, a mass of 3-11 Jupiter masses and an age between 60 Myr and 1 Gyr. This young age is consistent with the thin disk kinematics of the dwarf. The mass range overlaps with that usually considered to be planetary, despite this being an unbound object discovered in the field near the Sun. This apparently young rapid rotator is also undergoing vigorous atmospheric mixing, as determined by the IRAC and WISE-2 4.5 um photometry and the Saumon & Marley models. The optical spectrum for this 500 K object shows clearly detected lines of the neutral alkalis Cs and Rb, which are emitted from deep atmospheric layers with temperatures of 900-1200 K.

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Posts: 131433
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UGPS J072227.51-054031.2
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Title: FIRE Spectroscopy of the ultra-cool brown dwarf, UGPS J072227.51-054031.2: Kinematics, Rotation and Atmospheric Parameters
Authors: John J. Bochanski, Adam J. Burgasser, Robert A. Simcoe, Andrew A. West

We present {\lambda}/{\Delta}{\lambda} ~ 6000 near-infrared spectroscopy of the nearby T9 dwarf, UGPS J072227.51-054031.2, obtained during the commissioning of the Folded-Port Infrared Echellette Spectrograph on the Baade Magellan telescope at Las Campanas Observatory. The spectrum is marked by significant absorption from H2O, CH4 and H2. We also identify NH3 absorption features by comparing the spectrum to recently published line lists. The spectrum is fit with BT-Settl models, indicating Teff ~ 500-600 K and log g ~ 4.3-5.0. This corresponds to a mass of ~ 10-30 Jupiter masses and an age of 1-5 Gyr, however there are large discrepancies between the model and observed spectrum. The radial and rotational velocities of the brown dwarf are measured as 46.9 2.5 and 40 10 km/s, respectively, reflecting a thin disk Galactic orbit and fast rotation similar to other T dwarfs, suggesting a young, possibly planetary-mass brown dwarf.

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UGPS 0722-05
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Title: The discovery of a very cool, very nearby brown dwarf in the Galactic plane
Authors: Philip W. Lucas (1), C.G. Tinney (2), Ben Burningham (1), S. K. Leggett (3), David J. Pinfield (1), Richard Smart (4), Hugh R.A. Jones (1), Federico Marocco (4), Robert J. Barber (5), Sergei N. Yurchenko (6), Jonathan Tennyson (5), Miki Ishii (7), Motohide Tamura (8), Avril C. Day-Jones (9), Andrew Adamson (10), France Allard (11), Derek Homeier (12). ((1) University of Hertfordshire, (2) University of New South Wales, (3) Gemini Observatory, (4) Osservatorio Astronomico di Torino, (5) University College London, (6) Technische Universitat Dresden, (7) Subaru Telescope, (8) National Astronomical Observatory of Japan, (9) Universidad de Chile, (10) Joint Astronomy Centre, (11) Universite de Lyon, (12) Institut fur Astrophysik Gottingen.)
(Version v3)

We report the discovery of a very cool, isolated brown dwarf, UGPS 0722-05, with the UKIDSS Galactic Plane Survey. The near-infrared spectrum displays deeper H2O and CH4 troughs than the coolest known T dwarfs and an unidentified absorption feature at 1.275 um. We provisionally classify the object as a T10 dwarf but note that it may in future come to be regarded as the first example of a new spectral type. The distance is measured by trigonometric parallax as d=4.1{-0.5}{+0.6} pc, making it the closest known isolated brown dwarf. With the aid of Spitzer/IRAC we measure H-[4.5] = 4.71. It is the coolest brown dwarf presently known -- the only known T dwarf that is redder in H-[4.5] is the peculiar T7.5 dwarf SDSS J1416+13B, which is thought to be warmer and more luminous than UGPS 0722-05. Our measurement of the luminosity, aided by Gemini/T-ReCS N band photometry, is L = 9.2 3.1x10^{-7} Lsun. Using a comparison with well studied T8.5 and T9 dwarfs we deduce Teff=520 40 K. This is supported by predictions of the Saumon & Marley models. With apparent magnitude J=16.52, UGPS 0722-05 is the brightest T dwarf discovered by UKIDSS so far. It offers opportunities for future study via high resolution near-infrared spectroscopy and spectroscopy in the thermal infrared.

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RE: UGPSJ0722-05
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'Dark sun' is one of our nearest neighbours

A dim object less than 10 light years from Earth appears to be the closest brown dwarf yet found. The "star" is so cold that any residents on an orbiting planet would see a dark sun in their starry "daytime" sky.
The discovery suggests that brown dwarfs are common and that the objects could exist even closer to Earth.

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Date:
UGPS J0722-05
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Title: Discovery of a very cool brown dwarf amongst the ten nearest stars to the Solar System
Authors: Philip W. Lucas (1), C.G. Tinney (2), Ben Burningham (1), S. K. Leggett (3), David J. Pinfield (1), Richard Smart (4), Hugh R.A. Jones (1), Federico Marocco (4), Robert J. Barber (5), Sergei N. Yurchenko (6), Jonathan Tennyson (5), Miki Ishii (7), Motohide Tamura (8), Avril C. Day-Jones (9), Andrew Adamson (10). ((1) University of Hertfordshire, (2) University of New South Wales, (3) Gemini Observatory, (4) Osservatorio Astronomico di Torino, (5) University College London, (6) Technische Universitat Dresden, (7) Subaru Telescope, (8) National Astronomical Observatory of Japan, (9) Universidad de Chile, (10) Joint Astronomy Centre.)

Brown dwarfs are bodies with masses in the range between those of giant planets and the lightest stars. Some are isolated, while others orbit normal stars or exist in star clusters. Since 1995, more than 100 methane brown dwarfs, or T dwarfs, have been found with spectra similar to that of the planet Jupiter and effective temperatures in the range 500-1300 K. The detection of even cooler bodies will open up a new arena for atmospheric physics and help to determine the formation rate of stars and brown dwarfs in our Galaxy as a function of both mass and of time. Here we report the discovery in the UKIDSS Galactic Plane Survey of a brown dwarf, UGPS J0722-05, that is not only far less luminous and significantly cooler than previously known objects but also the nearest to the Solar System. The measured distance is 2.9 0.4 pc, from which we deduce an effective temperature in the range 400-500 K. The Gemini/NIRI near infrared spectrum displays deeper water vapour and methane absorption bands than the coolest known T dwarfs, and an unidentified absorption feature at 1.275 microns. Time will tell whether this object is regarded as a T10 dwarf or the first example of a new spectral type.

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Posts: 131433
Date:
UGPSJ0722-05
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UGPSJ0722-05 is a sub-brown dwarf located approximately nine light years from Earth. The astronomical object was discovered by Philip Lucas at the University of Hertfordshire in 2010.
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