CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with Keck/NIRES
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1.
California Institute of Technology
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 T_(eff) ≈ 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.
Copyright and License
© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
We thank Mike Line for providing a low-temperature extension of the LOWZ model grid, and we thank the anonymous referee for helpful comments that have improved this manuscript.
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.
The work of Grady Robbins and Aaron Meisner is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation.
Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication also makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration.
Facilities
WISE - Wide-field Infrared Survey Explorer, Keck:II -
Software References
SPLAT (Burgasser & the SPLAT DevelopmentTeam 2017), WiseView (Caselden et al. 2018), WSA (Hambly et al. 2008)
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Additional details
- ISSN
- 1538-4357
- 80NSSC21K148
- National Aeronautics and Space Administration
- AST-2007068
- National Science Foundation
- AST-2009136
- National Science Foundation
- AST-2009177
- National Science Foundation
- NSF's NOIRLab
- W. M. Keck Foundation
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)