We present the discovery of WISEA J083011.95+283716.0, the first Y dwarf candidate identified through the Backyard Worlds: Planet 9 citizen science project. We identified this object as a red, fast-moving source with a faint W2 detection in multi-epoch \textit{AllWISE} and unWISE images. We have characterized this object with Spitzer Space Telescope and \textit{Hubble Space Telescope} follow-up imaging. With mid-infrared detections in \textit{Spitzer}'s \emph{ch1} and \emph{ch2} bands and flux upper limits in Hubble Space Telescope F105W and F125W filters, we find that this object is both very faint and has extremely red colors (ch1−ch2=3.25±0.23 mag, F125W−ch2≥9.36 mag), consistent with a Teff∼300 K source, as estimated from the known Y dwarf population. A preliminary parallax provides a distance of 11.1−1.5+2.0 pc, leading to a slightly warmer temperature of ∼350 K. The extreme faintness and red Hubble Space Telescope and Spitzer Space Telescope colors of this object suggest it may be a link between the broader Y dwarf population and the coldest known brown dwarf WISE J0855−0714, and highlight our limited knowledge of the true spread of Y dwarf colors. We also present four additional Backyard Worlds: Planet 9 late-T brown dwarf discoveries within 30 pc.
@article{arxiv.2004.12829,
title = {WISEA J083011.95+283716.0: A Missing Link Planetary-Mass Object},
author = {Daniella C. Bardalez Gagliuffi and Jacqueline K. Faherty and Adam C. Schneider and Aaron Meisner and Dan Caselden and Guilluame Colin and Sam Goodman and J. Davy Kirkpatrick and Marc J. Kuchner and Jonathan Gagné and Sarah E. Logsdon and Adam J. Burgasser and Katelyn Allers and John Debes and John Wisniewski and Austin Rothermich and Nikolaj S. Andersen and Melina Thévenot and Jim Walla},
journal= {arXiv preprint arXiv:2004.12829},
year = {2020}
}