The Enigmatic Brown Dwarf WISEA J153429.75-104303.3 (a.k.a. "The Accident")

July 2021 • 2021ApJ...915L...6K

Authors • Kirkpatrick, J. Davy • Marocco, Federico • Caselden, Dan • Meisner, Aaron M. • Faherty, Jacqueline K. • Schneider, Adam C. • Kuchner, Marc J. • Casewell, S. L. • Gelino, Christopher R. • Cushing, Michael C. • Eisenhardt, Peter R. • Wright, Edward L. • Schurr, Steven D.

Abstract • Continued follow-up of WISEA J153429.75-104303.3, announced in Meisner et al., has proven it to have an unusual set of properties. New imaging data from Keck/MOSFIRE and HST/WFC3 shows that this object is one of the few faint proper motion sources known with J - ch2 >8 mag, indicating a very cold temperature consistent with the latest known Y dwarfs. Despite this, it has W1-W2 and ch1-ch2 colors ~1.6 mag bluer than a typical Y dwarf. A new trigonometric parallax measurement from a combination of WISE, Spitzer, and HST astrometry confirms a nearby distance of ${16.3}_{-1.2}^{+1.4}$ pc and a large transverse velocity of 207.4 ± 15.9 km s^-1. The absolute J, W2, and ch2 magnitudes are in line with the coldest known Y dwarfs, despite the highly discrepant W1-W2 and ch1-ch2 colors. We explore possible reasons for the unique traits of this object and conclude that it is most likely an old, metal-poor brown dwarf and possibly the first Y subdwarf. Given that the object has an HST F110W magnitude of 24.7 mag, broadband spectroscopy and photometry from JWST are the best options for testing this hypothesis.

Links

• PREPRINT http://arxiv.org/abs/2106.13408
• ELECTR https://doi.org/10.3847%2F2041-8213%2Fac0437
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2021ApJ...915L...6K
• PDF https://iopscience.iop.org/article/10.3847/2041-8213/ac0437/pdf
• DATA https://irsa.ipac.caltech.edu/bibdata/2021/K/2021ApJ...915L...6K.html