Discovery of the Y1 Dwarf WISE J064723.23-623235.5

TL;DR

This paper reports the discovery and characterization of WISE J064723.23-623235.5, a nearby, very cold Y1 brown dwarf, using infrared data and spectroscopy, providing insights into its physical properties and potential group membership.

Contribution

It presents the identification and detailed analysis of a new Y1 brown dwarf, including its spectral classification, temperature, mass estimate, and possible association with a stellar moving group.

Findings

Spectral type Y1+/-0.5, one of the latest Y dwarfs classified.

Effective temperature estimated at 350-400K.

Possible membership in the Columba moving group, suggesting a very young age.

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 pi = 115+/-12 mas (d = 8.7+/-0.9 pc) and proper motion of mu = 387+/-25 mas/yr based on 2.5 years 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 350-400K 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.