Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf

February 2023 • 2023ApJ...943L..16S

Authors • Schneider, Adam C. • Burgasser, Adam J. • Bruursema, Justice • Munn, Jeffrey A. • Vrba, Frederick J. • Caselden, Dan • Kabatnik, Martin • Rothermich, Austin • Sainio, Arttu • Bickle, Thomas P. • Dahm, Scott E. • Meisner, Aaron M. • Kirkpatrick, J. Davy • Suárez, Genaro • Gagné, Jonathan • Faherty, Jacqueline K. • Vos, Johanna M. • Kuchner, Marc J. • Williams, Stephen J. • Bardalez Gagliuffi, Daniella • Aganze, Christian • Hsu, Chih-Chun • Theissen, Christopher • Cushing, Michael C. • Marocco, Federico • Casewell, Sarah • Backyard Worlds: Planet 9 Collaboration

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 CH4 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 L8γ-T0γ. We tentatively find that CWISE J0506+0738 is variable at 3-5 μm 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.


IPAC Authors


Davy Kirkpatrick

Senior Scientist

Federico Marocco

Assistant Scientist