Indications of Water Clouds in the Coldest Known Brown Dwarf
Abstract
We present a deep near-infrared image of the newly discovered brown dwarf WISE J085510.83-071442.5 (W0855) using the FourStar imager at Las Campanas Observatory. Our detection of J3 = 24.8^{+0.53}_{-0.35} (J MKO = 25.0^{+0.53}_{-0.35}) at 2.6σ—or equivalently an upper limit of J3 > 23.8 (J MKO > 24.0) at 5σ makes W0855 the reddest brown dwarf ever categorized (J MKO - W2 = 10.984^{+0.53}_{-0.35} at 2.6σ—or equivalently an upper limit of J MKO - W2 > 9.984 at 5σ) and refines its position on color-magnitude diagrams. Comparing the new photometry with chemical equilibrium model atmosphere predictions, we demonstrate that W0855 is 2.7σ from models using a cloudless atmosphere and well reproduced by partly cloudy models (50%) containing sulfide and water ice clouds. Non-equilibrium chemistry or non-solar metallicity may change predictions, however using currently available model approaches, this is the first candidate outside our own solar system to have direct evidence for water clouds.
This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2014
- DOI:
- 10.1088/2041-8205/793/1/L16
- arXiv:
- arXiv:1408.4671
- Bibcode:
- 2014ApJ...793L..16F
- Keywords:
-
- brown dwarfs;
- infrared: stars;
- proper motions;
- solar neighborhood;
- stars: individual: WISE J085510.83-071442.5;
- stars: low-mass;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in ApJ Letters. Eight pages, 3 Figures