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

Kirkpatrick, J. Davy and Marocco, Federico and Caselden, Dan and Meisner, Aaron M. and Faherty, Jacqueline K. and Schneider, Adam C. and Kuchner, Marc J. and Casewell, S. L. and Gelino, Christopher R. and Cushing, Michael C. and Eisenhardt, Peter R. and Wright, Edward L. and Schurr, Steven D. (2021) Enigmatic Brown Dwarf WISEA J153429.75-104303.3 (a.k.a. "The Accident"). Astrophysical Journal Letters, 915 (1). Art. No. L6. ISSN 2041-8205. doi:10.3847/2041-8213/ac0437.

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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^(+1.4)_(-1.2) 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kirkpatrick, J. Davy0000-0003-4269-260X
Marocco, Federico0000-0001-7519-1700
Caselden, Dan0000-0001-7896-5791
Meisner, Aaron M.0000-0002-1125-7384
Faherty, Jacqueline K.0000-0001-6251-0573
Schneider, Adam C.0000-0002-6294-5937
Kuchner, Marc J.0000-0002-2387-5489
Casewell, S. L.0000-0003-2478-0120
Cushing, Michael C.0000-0001-7780-3352
Wright, Edward L.0000-0001-5058-1593
Schurr, Steven D.0000-0003-1785-5550
Additional Information:© 2021. The American Astronomical Society. Received 2021 May 10; revised 2021 May 18; accepted 2021 May 21; published 2021 June 30. This research is based on observations made under program 16243 with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This publication makes use of data products from WISE/NEOWISE, which is a joint project of UCLA and JPL/Caltech, funding by NASA. Portions of this research were carried out at JPL/Caltech under contract with NASA. J.K.F. thanks the Heising Simons Foundation for research support. Facilities: HST (WFC3) - , Keck:I (MOSFIRE) - , WISE - , NEOWISE - Software: WiseView (Caselden et al. 2018).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
W. M. Keck FoundationUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Subject Keywords:Stellar types; T dwarfs; Y dwarfs; Proper motions; Metallicity
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Stellar types (1634); T dwarfs (1679); Y dwarfs (1827); Proper motions (1295); Metallicity (1031)
Record Number:CaltechAUTHORS:20210716-220506187
Persistent URL:
Official Citation:J. Davy Kirkpatrick et al 2021 ApJL 915 L6
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109888
Deposited By: Tony Diaz
Deposited On:16 Jul 2021 22:15
Last Modified:16 Jul 2021 22:15

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