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Title: CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with Keck/NIRES
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 theJband, no standard matches well across the fullYJHKwavelength 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 andTeff≈ 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 3–5μm color.  more » « less
Award ID(s):
2219090 2009136 2238468
PAR ID:
10474175
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
958
Issue:
1
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 94
Size(s):
Article No. 94
Sponsoring Org:
National Science Foundation
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