The First JWST Spectral Energy Distribution of a Y Dwarf

Abstract We present the first JWST spectral energy distribution of a Y dwarf. This Y0 dwarf WISE J035934.06−540154.6 consists low-resolution ( λ /Δ ∼100) spectroscopy from 1–12 μ m and three photometric points at 15, 18, 21 m. The spectrum exhibits numerous fundamental, overtone, combination rotational–vibrational bands H 2 O, CH 4 , CO, CO NH 3 including previously unidentified ν band Using Rayleigh–Jeans tail to account for flux emerging wavelengths greater than m, we measure bolometric luminosity 1.523 ± 0.090 × 10 20 W. determine semiempirical effective temperature estimate 467 − 18 + 16 K using evolutionary models radius. Finally, compare photometry grid atmospheric find reasonably good agreement with model having T eff = 450 K, log g 3.25 [cm s −2 ], [M/H] −0.3. However, low surface gravity implies an extremely mass 1 M Jup very young age Myr, latter which is inconsistent simulations volume-limited samples cool brown dwarfs.