2013ApJ...776..128K

We present the discovery of a very cold, very low mass, nearby brown dwarf using data from the NASA Wide-field Infrared Survey Explorer (WISE). The object, WISE J064723.23-623235.5, has a very red WISE color of W1-W2 > 3.77 mag and a very red Spitzer Space Telescope color of ch1-ch2 = 2.82 ±0.09 mag. In J_MKO-ch2 color (7.58±0.27 mag) it is one of the two or three reddest brown dwarfs known. Our grism spectrum from the Hubble Space Telescope (HST) confirms it to be the seventeenth Y dwarf discovered, and its spectral type of Y1±0.5 makes it one of the four latest-type Y dwarfs classified. Astrometric imaging from Spitzer and HST, combined with data from WISE, provides a preliminary parallax of π = 115±12 mas (d = 8.7 ±0.9 pc) and proper motion of µ = 387±25 mas/yr based on 2.5 yr of monitoring. The spectrum implies a blue J-H color, for which model atmosphere calculations suggest a relatively low surface gravity. The best fit to these models indicates an effective temperature of 350-400 K and a mass of ∼5-30 M_Jup. Kinematic analysis hints that this object may belong to the Columba moving group, which would support an age of ∼30 Myr and thus an even lower mass of <2 M_Jup, but verification would require a radial velocity measurement not currently possible for a J = 22.7 mag brown dwarf.