Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf
Adam C. Schneider, Adam J. Burgasser, Justice Bruursema, Jeffrey A. Munn, F. J. Vrba, Dan Caselden, Martin Kabatnik, Austin Rothermich, Arttu Sainio, Thomas P. Bickle, S. E. Dahm, Aaron Meisner, J. Davy Kirkpatrick, Genaro Suárez, Jonathan Gagné, Jacqueline K. Faherty, Johanna M. Vos, Marc J. Kuchner, Stephen J. Williams, Daniella C. Bardalez Gagliuffi, Christian Aganze, Chih-Chun Hsu, Christopher A. Theissen, Michael C. Cushing, Federico Marocco, S. L. Casewell
Abstract
Abstract We present the discovery of CWISE J050626.96+073842.4 (CWISE J0506+0738), an L/T transition dwarf with extremely red near-infrared colors discovered through the Backyard Worlds: Planet 9 citizen science project. Photometry from UKIRT and CatWISE give a ( J − K ) MKO color of 2.97 ± 0.03 mag and a J MKO − W2 color of 4.93 ± 0.02 mag, making CWISE J0506+0738 the reddest known free-floating L/T dwarf in both colors. We confirm the extremely red nature of CWISE J0506+0738 using Keck/NIRES near-infrared spectroscopy and establish that it is a low-gravity, late-type L/T transition dwarf. The spectrum of CWISE J0506+0738 shows possible signatures of CH 4 absorption in its atmosphere, suggesting a colder effective temperature than other known, young, red L dwarfs. We assign a preliminary spectral type for this source of L8 γ –T0 γ . We tentatively find that CWISE J0506+0738 is variable at 3–5 μ m based on multiepoch WISE photometry. Proper motions derived from follow-up UKIRT observations combined with a radial velocity from our Keck/NIRES spectrum and a photometric distance estimate indicate a strong membership probability in the β Pic moving group. A future parallax measurement will help to establish a more definitive moving group membership for this unusual object.