CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with Keck/NIRES

ORAL

Abstract

Y dwarfs, the coolest known spectral class of brown dwarfs, overlap in mass and temperature with giant exoplanets, providing unique laboratories for studying low-temperature atmospheres. However, only a fraction of Y dwarf candidates have been spectroscopically confirmed. We present Keck/NIRES near-infrared spectroscopy of the nearby (d ~ 6-8 pc) brown dwarf CWISE J105512.11+544328.3. Although its near-infrared spectrum aligns best with the Y0 standard in the J-band, no standard matches well across the full YJHK wavelength range. The CWISE J105512.11+544328.3 NH3-H = 0.427 ± 0.0012 and CH4-J = 0.0385 ± 0.0007 absorption indices and absolute Spitzer [4.5] magnitude of 15.18 ± 0.22 are also indicative of an early Y dwarf rather than a late T dwarf. CWISE J105512.11+544328.3 additionally exhibits the bluest Spitzer [3.6]–[4.5] color among all spectroscopically confirmed Y dwarfs. Despite this anomalously blue Spitzer color given its low luminosity, CWISE J105512.11+544328.3 does not show other clear kinematic or spectral indications of low metallicity. Atmospheric model comparisons yield a log(g) ≤ 4.5 and Teff ≈ 500 ± 150 K for this source. We classify CWISE J105512.11+544328.3 as a Y0 (pec) dwarf, adding to the remarkable diversity of the Y-type population. JWST spectroscopy would be crucial to understanding the origin of this Y dwarf's unusual preference for low-gravity models and blue 3-5 μm color.

*This work has been supported in part by the NASA Citizen Science Seed Funding Program, Grant 80NSSC21K1485. This material is based upon work supported by the National Science Foundation under Grant No. 2007068, 2009136, and 2009177.

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Publication: Robbins, G. et al. 2023, "CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with
Keck/NIRES", The Astrophysical Journal, AAS 958 94.

Presenters

  • Grady D Robbins

    • University of Florida
    • University of Florida, NSF's National Optical-Infrared Research Laboratory

Authors

  • Grady D Robbins

    • University of Florida
    • University of Florida, NSF's National Optical-Infrared Research Laboratory

  • Aaron Meisner

    • NSF's National Optical-Infrared Research Laboratory

  • Adam Schneider

    • United States Naval Observatory

  • Adam Burgasser

    • University of California San Diego

  • J. D Kirkpatrick

    • IPAC

  • Jonathan Gagnè

    • Planetarium Rio Tinto Alcan

  • Chih-Chun Hsu

    • Northwestern University

  • Leslie Moranta

    • Planetarium Rio Tinto Alcan,

  • Sarah Casewell

    • University of Leicester

  • Federico Marocco

    • IPAC

  • Roman Gerasimov

    • University of California San Diego

  • Jacqueline Faherty

    • American Museum of Natural History

  • Marc Kuchner

    • NASA Goddard Space Flight Center

  • Dan Caselden

    • American Museum of Natural History

  • Michael Cushing

    • University of Toledo

  • Sherelyn Alejandro

    • City University of New York