Discovery of the Y1 Dwarf WISE J064723.23-623235.5

October 2013 • 2013ApJ...776..128K

Authors • Kirkpatrick, J. Davy • Cushing, Michael C. • Gelino, Christopher R. • Beichman, Charles A. • Tinney, C. G. • Faherty, Jacqueline K. • Schneider, Adam • Mace, Gregory N.

Abstract • 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^-1 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.

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IPAC Authors
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Chris Gelino

Associate Scientist

Davy Kirkpatrick

Senior Scientist