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

Abstract

We present the discovery of CWISE J052306.42$-$015355.4, which was found as a faint, significant proper motion object (0.52 $\pm$ 0.08 arcsec yr${}^{-1}$) using machine learning tools on the unWISE re-processing on 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 vs. $J-$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 $\le$ 68 pc, which results in a tangential velocity of $\le$ 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.

arXiv comment7 pages, 3 figures, accepted for publication in the AJ

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• Exploring the Extremes: Characterizing a New Population of Old and Cold Brown Dwarfs