The Collapse of the Wien Tail in the Coldest Brown Dwarf?

The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5

Authors:

Schneider et al

Abstract:

We present Hubble Space Telescope (HST) near-infrared photometry of the coldest known brown dwarf, WISE J085510.83−071442.5 (WISE 0855−0714). WISE 0855−0714 was observed with the Wide Field Camera 3 (WFC3) aboard HST using the F105W, F125W, and F160W filters, which approximate the Y, J, and H near-infrared bands. WISE 0855−0714 is undetected at F105W with a corresponding 2σ magnitude limit of ∼26.9. We marginally detect WISE 0855−0714 in the F125W images (S/N ∼4), with a measured magnitude of 26.41 ± 0.27, more than a magnitude fainter than the J−band magnitude reported by Faherty and coworkers. WISE J0855−0714 is clearly detected in the F160W band, with a magnitude of 23.90 ± 0.02, the first secure detection of WISE 0855−0714 in the near-infrared. Based on these data, we find that WISE 0855−0714 has extremely red F105W−F125W and F125W−F160W colors relative to other known Y dwarfs. We find that when compared to the models of Saumon et al. and Morley et al., the F105W−F125W and F125W−F160W colors of WISE 0855−0714 cannot be accounted for simultaneously. These colors likely indicate that we are seeing the collapse of flux on the Wien tail for this extremely cold object.

WISE 0855−0714 is the Coldest Brown Dwarf

Temperature constraints on the coldest brown dwarf known WISE 0855-0714

Authors:

Beamín et al

Abstract:

Context.

Nearby isolated planetary mass objects are beginning to be discovered, but their individual properties are poorly constrained because their low surface temperatures and strong molecular self-absorption make them extremely faint.

Aims.

We aimed to detect the near infrared emission of the coldest brown dwarf (BD) found so far WISE0855−0714, located ∼2.2 pc away, and to improve its temperature estimate (Teff= 225-260 K) from a comparison with state of the art models of BD atmospheres.
Methods. We observed the field containing WISE0855-0714 with HAWK-I at the VLT in the Y band. For BDs with Teff less than 500 K theoretical models predict strong signal (or rather less molecular absorption) in this band.

Results.

WISE0855-0714 was not detected in our Y-band images, thus placing an upper limit on its brightness to Y greater than 24.4 mag at 3-σ level, leading to Y-[4.5] greater than 10.5. Combining this limit with previous detections and upper limits at other wavelengths, WISE0855-0714 is confirmed as the reddest BD detected. We applied spectral energy distribution fitting with collections of models from two independent groups for extremely cool BD atmospheres leading to an effective temperature of Teff less than 250 K, making WISE0855-0714 the coldest BD discovered to date.