The discovery of a very cool, very nearby brown dwarf in the Galactic plane
Abstract
We report the discovery of a very cool, isolated brown dwarf, UGPS 0722-05, with the United Kingdom Infrared Telescope Deep Sky Survey (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 μm. 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+0.6-0.5 pc, making it the closest known isolated brown dwarf. With the aid of Spitzer/Infrared Array Camera (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 +/- 3.1 × 10-7Lsolar. 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 of the ~90 T dwarfs discovered by UKIDSS so far. It offers opportunities for future study via high-resolution near-infrared spectroscopy and spectroscopy in the thermal infrared.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2010
- DOI:
- 10.1111/j.1745-3933.2010.00927.x
- arXiv:
- arXiv:1004.0317
- Bibcode:
- 2010MNRAS.408L..56L
- Keywords:
-
- surveys;
- brown dwarfs;
- stars: low mass;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Accepted by MNRAS Letters. Note that preliminary parallax measurement changed significantly after version 1 so the paper was withdrawn from Nature