NEOWISE-R Observation of the Coolest Known Brown Dwarf

TL;DR

This paper reports NEOWISE-R observations confirming the extremely low temperature, high proper motion, and large parallax of the coldest known brown dwarf, refining its astrometric measurements.

Contribution

The study provides updated astrometric data for WISE J085510.83-071442.5 using NEOWISE-R, improving measurements of its parallax and proper motion compared to previous data.

Findings

Confirmed the brown dwarf's low temperature (~250 K)

Refined parallax to 448 +/- 33 mas

Measured high proper motion of about 8.1 arcsec/yr

Abstract

The Wide-field Infrared Survey Explorer (WISE) spacecraft has been reactivated as NEOWISE-R to characterize and search for Near Earth Objects. The brown dwarf WISE J085510.83-071442.5 has now been reobserved by NEOWISE-R, and we confirm the results of Luhman (2014b), who found a very low effective temperature ($\approx 250$ K), a very high proper motion (8.1 +/- 0.1 arcsec/yr) , and a large parallax (454 +/- 45 mas). The large proper motion has separated the brown dwarf from the background sources that influenced the 2010 WISE data, allowing a measurement of a very red WISE color of W1-W2 $> 3.9$ mag. A re-analysis of the 2010 WISE astrometry using only the W2 band, combined with the new NEOWISE-R 2014 position, gives an improved parallax of 448 +/- 33 mas and proper motion of 8.08 +/- 0.05\; arcsec/yr. These are all consistent with Luhman (2014b).