Journal ArticleDiscovery of the Remarkably Red L/T Transition Object VHS J183135.58-551355.9Bickle, Thomas P; Schneider, Adam C; Gagné, Jonathan; Faherty, Jacqueline K; Rothermich, Austin; Vos, Johanna M; Suárez, Genaro; Kirkpatrick, J Davy; Meisner, Aaron M; Kuchner, Marc J; Burgasser, Adam J; Marocco, Federico; Casewell, Sarah L; Caselden, Dan; Bardalez_Gagliuffi, Daniella CThe_Backyard_Worlds_Planet_9_Collaboration<title>Abstract</title> <p>We present the discovery of VHS J183135.58−551355.9 (hereafter VHS J1831−5513), an L/T transition dwarf identified as a result of its unusually red near-infrared colors (<italic>J</italic>−<italic>K</italic>_S= 3.633 ± 0.277 mag;<italic>J</italic>−<italic>W</italic>2 = 6.249 ± 0.245 mag) from the VISTA Hemisphere Survey and CatWISE2020 surveys. We obtain low-resolution near-infrared spectroscopy of VHS J1831−5513 using the Magellan Folded port InfraRed Echellette spectrograph to confirm its extremely red nature and assess features sensitive to surface gravity (i.e., youth). Its near-infrared spectrum shows multiple CH₄absorption features, indicating an exceptionally low effective temperature for its spectral type. Based on proper-motion measurements from CatWISE2020 and a photometric distance derived from its<italic>K</italic>_{<italic>s</italic>}-band magnitude, we find that VHS J1831−5513 is a likely (∼85% probability) kinematic member of the<italic>β</italic>Pictoris moving group. Future radial velocity and trigonometric parallax measurements will clarify such membership. Follow-up mid-infrared or higher-resolution near-infrared spectroscopy of this object will allow for further investigation as to the cause(s) of its redness, such as youth, clouds, and viewing geometry.</p>IOP2024-07-0910533770The Astronomical Journal1682660004-6256https://doi.org/10.3847/1538-3881/ad4b162009136; 1909776; 2009177; 2238468National Science Foundation