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

journal contribution
posted on 13.07.2021, 15:45 by J Davy Kirkpatrick, Federico Marocco, Dan Caselden, Aaron M Meisner, Jacqueline K Faherty, Adam C Schneider, Marc J Kuchner, SL Casewell, Christopher R Gelino, Michael C Cushing, Peter R Eisenhardt, Edward L Wright, Steven D Schurr
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.

History

Citation

ApJL 915 L6

Author affiliation

Department of Physics and Astronomy

Version

AM (Accepted Manuscript)

Published in

The Astrophysical Journal Letters

Volume

915

Issue

1

Pagination

L6

Publisher

American Astronomical Society

issn

2041-8205

eissn

2041-8213

Acceptance date

21/05/2021

Copyright date

2021

Available date

30/06/2022

Language

en