Using two epochs of 4.5 μm images from the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope, we recently identified a common proper motion companion to the white dwarf WD0806-661 that is a candidate for the coldest known brown dwarf. To verify its cool nature, we have obtained images of this object at 3.6 μm with IRAC, at J with the High Acuity Wide-field K-band Imager (HAWK-I) on the Very Large Telescope, and in a filter covering the red half of J with FourStar on Magellan. WD0806-661B is detected by IRAC but not HAWK-I or FourStar. From these data we measure colors of [3.6] - [4.5] = 2.77 0.16 and J - [4.5] > 7.0 (S/N < 3). Based on these colors and its absolute magnitudes, WD0806-661B is the coldest companion directly imaged outside of the solar system and is a contender for the coldest known brown dwarf with the Y dwarf WISEPJ1828+2650. It is unclear which of these two objects is colder given the available data. A comparison of its absolute magnitude at 4.5 μm to the predictions of theoretical spectra and evolutionary models suggests that WD0806-661B has T eff = 300-345K.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science