Discovery of CWISE J052306.42−015355.4, an Extreme T Subdwarf Candidate

Creators: Brooks, Hunter; Kirkpatrick, J. Davy; Caselden, Dan; Schneider, Adam C.; Meisner, Aaron M.; Faherty, Jacqueline K.; Casewell, S. L.; Kuchner, Marc J.; The Backyard Worlds: Planet 9 Collaboration

Abstract

We present the discovery of CWISE J052306.42−015355.4, which was found as a faint, significant proper-motion object (0.″52 ± 0.″08 yr⁻¹) using machine-learning tools on the unWISE re-processing of time series images from the Wide-field Infrared Survey Explorer. Using the CatWISE2020 W1 and W2 magnitudes along with a J-band detection from the VISTA Hemisphere Survey, the location of CWISE J052306.42−015355.4 on the W1 − W2 versus J − W2 diagram best matches that of other known, or suspected, extreme T subdwarfs. As there is currently very little knowledge concerning extreme T subdwarfs we estimate a rough distance of ≤68 pc, which results in a tangential velocity of ≤167 km s⁻¹, both of which are tentative. A measured parallax is greatly needed to test these values. We also estimate a metallicity of −1.5 < [M/H] < −0.5 using theoretical predictions.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 August 19; revised 2021 November 11; accepted 2021 November 14; published 2022 January 7. Backyard Worlds research was supported by NASA grant 2017-ADAP17-0067 and by the NSF under grants AST- 2007068, AST-2009177, and AST-2009136. SLC is supported by an STFC Ernest Rutherford Research Fellowship. We want to thank the Student Astrophysics Society 10 for providing the resources that enabled the pairing of high school and undergraduate students with practicing astronomers and advanced citizen scientists. This work makes use of data products from WISE/NEOWISE, which is a joint project of UCLA and JPL/Caltech, funding by NASA. The CatWISE effort is led by the Jet Propulsion Laboratory, California Institute of Technology, with funding from NASAs Astrophysics Data Analysis Program. We thank the anonymous referee, whose valuable comments helped improve the manuscript. Software: WiseView (Caselden et al. 2018).

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