Disentangling disc and atmospheric signatures of young brown dwarfs with JWST/NIRSpec

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Volume 703 (November 2025)

A&A, 703 (2025) A65

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Table C.1

Summary of the free parameters and the retrieved values with 1σ uncertainties. The prior ranges and the distributions used (uniform or normal) are indicated.

Parameter	Description	Prior Range	TWA27A	TWA28
R_p	Radius in Jupiter radii	𝒰(2.2, 3.8)	$+ {3.084}_{- 0.005}^{+ 0.005}$ $\[+3.084_{-0.005}^{+0.005}\]$	$+ {3.096}_{- 0.004}^{+ 0.003}$ $\[+3.096_{-0.004}^{+0.003}\]$
v_rad/km s⁻¹	Radial velocity	𝒰(−30, 30)	$+ {7.98}_{- 0.12}^{+ 0.12}$ $\[+7.98_{-0.12}^{+0.12}\]$	$+ {11.26}_{- 0.07}^{+ 0.07}$ $\[+11.26_{-0.07}^{+0.07}\]$
log g	Surface gravity of the atmosphere	𝒰(3.0, 4.5)	$+ {4.32}_{- 0.03}^{+ 0.03}$ $\[+4.32_{-0.03}^{+0.03}\]$	$+ {4.44}_{- 0.02}^{+ 0.02}$ $\[+4.44_{-0.02}^{+0.02}\]$
T₀	Temperature at the bottom of the atmosphere	𝒰(3000, 8000)	$+ 3496_{- 23}^{+ 34}$ $\[+3496_{-23}^{+34}\]$	$+ 3367_{- 12}^{+ 14}$ $\[+3367_{-12}^{+14}\]$
log P_RCE/bar	Pressure at radiative-convective equilibrium	𝒰(−3.0, 1.0)	$- {1.15}_{- 0.05}^{+ 0.05}$ $\[-1.15_{-0.05}^{+0.05}\]$	$- {0.75}_{- 0.04}^{+ 0.02}$ $\[-0.75_{-0.04}^{+0.02}\]$
log ΔP_low/bar	Pressure spacing for lower atmosphere layers	𝒰(0.2, 1.6)	$+ {0.47}_{- 0.03}^{+ 0.04}$ $\[+0.47_{-0.03}^{+0.04}\]$	$+ {0.24}_{- 0.02}^{+ 0.03}$ $\[+0.24_{-0.02}^{+0.03}\]$
log ΔP_high/bar	Pressure spacing for upper atmosphere layers	𝒰(0.2, 1.6)	$+ {1.44}_{- 0.09}^{+ 0.08}$ $\[+1.44_{-0.09}^{+0.08}\]$	$+ {1.13}_{- 0.10}^{+ 0.11}$ $\[+1.13_{-0.10}^{+0.11}\]$
∇_T,0	Temperature gradient at P₀ = 100 bar	𝒰(0.04, 0.38)	< +0.040	< +0.040
∇_T,1	Temperature gradient at P₁ = P_RCE − 2ΔP_low	𝒰(0.04, 0.38)	$+ {0.044}_{- 0.002}^{+ 0.003}$ $\[+0.044_{-0.002}^{+0.003}\]$	$+ {0.042}_{- 0.001}^{+ 0.001}$ $\[+0.042_{-0.001}^{+0.001}\]$
∇_T,2	Temperature gradient at P₂ = P_RCE − 1ΔP_low	𝒰(0.04, 0.38)	$+ {0.124}_{- 0.002}^{+ 0.002}$ $\[+0.124_{-0.002}^{+0.002}\]$	$+ {0.122}_{- 0.002}^{+ 0.002}$ $\[+0.122_{-0.002}^{+0.002}\]$
∇_T,3	Temperature gradient at P₃ = P_RCE + 1ΔP_high	𝒰(0.00, 0.38)	$+ {0.036}_{- 0.004}^{+ 0.004}$ $\[+0.036_{-0.004}^{+0.004}\]$	$+ {0.072}_{- 0.004}^{+ 0.004}$ $\[+0.072_{-0.004}^{+0.004}\]$
∇_T,4	Temperature gradient at P₄ = P_RCE + 2ΔP_high	𝒰(0.00, 0.38)	$+ {0.121}_{- 0.008}^{+ 0.005}$ $\[+0.121_{-0.008}^{+0.005}\]$	$+ {0.055}_{- 0.005}^{+ 0.004}$ $\[+0.055_{-0.005}^{+0.004}\]$
∇_T,5	Temperature gradient at P₅ = 10⁻⁵ bar	𝒰(0.00, 0.38)	$+ {0.113}_{- 0.015}^{+ 0.010}$ $\[+0.113_{-0.015}^{+0.010}\]$	$+ {0.006}_{- 0.004}^{+ 0.005}$ $\[+0.006_{-0.004}^{+0.005}\]$
∇_T,RCE	Temperature gradient at P_RCE	𝒰(0.04, 0.38)	$+ {0.128}_{- 0.001}^{+ 0.002}$ $\[+0.128_{-0.001}^{+0.002}\]$	$+ {0.127}_{- 0.002}^{+ 0.002}$ $\[+0.127_{-0.002}^{+0.002}\]$
log R^bb/R_jup	Effective radius of the blackbody emission	𝒰(0, 2)	$+ {1.077}_{- 0.006}^{+ 0.005}$ $\[+1.077_{-0.006}^{+0.005}\]$	$+ {1.142}_{- 0.003}^{+ 0.003}$ $\[+1.142_{-0.003}^{+0.003}\]$
$T_{eff}^{b b} / K$ $\[T_{\text {eff }}^{\mathrm{bb}} / \mathrm{K}\]$	Temperature of the blackbody emission	𝒰(300, 900)	$+ {642.91}_{- 3.71}^{+ 4.02}$ $\[+642.91_{-3.71}^{+4.02}\]$	$+ {653.20}_{- 1.91}^{+ 1.93}$ $\[+653.20_{-1.91}^{+1.93}\]$
log R^slab/R_jup	Effective radius of the slab model	𝒰(0, 3)	$+ {0.861}_{- 0.017}^{+ 0.022}$ $\[+0.861_{-0.017}^{+0.022}\]$	$+ {1.448}_{- 0.122}^{+ 0.148}$ $\[+1.448_{-0.122}^{+0.148}\]$
$\log N_{mol}^{slab} / {c m}^{- 2}$ $\[\log~ N_{\text {mol}}^{\text {slab}} / \mathrm{cm}^{-2}\]$	Column density of slab model	𝒰(14, 18)	$+ {17.33}_{- 0.08}^{+ 0.06}$ $\[+17.33_{-0.08}^{+0.06}\]$	$+ {15.98}_{- 0.31}^{+ 0.26}$ $\[+15.98_{-0.31}^{+0.26}\]$
$\log T_{ex}^{slab} / K$ $\[\log~ T_{\text {ex}}^{\text {slab}} / \mathrm{K}\]$	Excitation temperature of slab model	𝒰(2.7, 3.3)	>+3.300	$+ {3.227}_{- 0.009}^{+ 0.009}$ $\[+3.227_{-0.009}^{+0.009}\]$
v^slab/km s⁻¹	Radial velocity of disc emission	𝒰(−60, 60)	$- {0.34}_{- 1.60}^{+ 1.58}$ $\[-0.34_{-1.60}^{+1.58}\]$	$+ {7.62}_{- 0.88}^{+ 0.90}$ $\[+7.62_{-0.88}^{+0.90}\]$
log l_G/km s⁻¹	Global correlation length	𝒰(1.4, 2.6)	$+ {1.901}_{- 0.015}^{+ 0.016}$ $\[+1.901_{-0.015}^{+0.016}\]$	$+ {1.900}_{- 0.011}^{+ 0.013}$ $\[+1.900_{-0.011}^{+0.013}\]$
log b(g140h)	Error scaling factor for G140H grating	𝒰(0, 3)	$+ {1.62}_{- 0.16}^{+ 0.16}$ $\[+1.62_{-0.16}^{+0.16}\]$	$+ {1.85}_{- 0.05}^{+ 0.05}$ $\[+1.85_{-0.05}^{+0.05}\]$
log b(g235h)	Error scaling factor for G235H grating	𝒰(0, 3)	$+ {1.92}_{- 0.05}^{+ 0.04}$ $\[+1.92_{-0.05}^{+0.04}\]$	$+ {1.88}_{- 0.02}^{+ 0.02}$ $\[+1.88_{-0.02}^{+0.02}\]$
log b(g395h)	Error scaling factor for G395H grating	𝒰(0, 3)	$+ {1.17}_{- 0.17}^{+ 0.15}$ $\[+1.17_{-0.17}^{+0.15}\]$	$+ {1.32}_{- 0.03}^{+ 0.03}$ $\[+1.32_{-0.03}^{+0.03}\]$
α_12CO	Deviation from chemical equilibrium for ¹²CO	𝒩(0, 1)	$+ {0.16}_{- 0.03}^{+ 0.03}$ $\[+0.16_{-0.03}^{+0.03}\]$	$+ {0.39}_{- 0.02}^{+ 0.02}$ $\[+0.39_{-0.02}^{+0.02}\]$
α_H2O	Deviation from chemical equilibrium for H₂O	𝒩(0, 1)	$+ {0.43}_{- 0.03}^{+ 0.03}$ $\[+0.43_{-0.03}^{+0.03}\]$	$+ {0.55}_{- 0.02}^{+ 0.02}$ $\[+0.55_{-0.02}^{+0.02}\]$
α_SiO	Deviation from chemical equilibrium for SiO	𝒩(0, 1)	$+ {0.26}_{- 0.04}^{+ 0.04}$ $\[+0.26_{-0.04}^{+0.04}\]$	$+ {0.43}_{- 0.02}^{+ 0.03}$ $\[+0.43_{-0.02}^{+0.03}\]$
α_CO2	Deviation from chemical equilibrium for CO₂	𝒩(0, 1)	$+ {0.37}_{- 0.04}^{+ 0.04}$ $\[+0.37_{-0.04}^{+0.04}\]$	$+ {0.31}_{- 0.03}^{+ 0.03}$ $\[+0.31_{-0.03}^{+0.03}\]$
α_TiO	Deviation from chemical equilibrium for TiO	𝒩(0, 1)	$- {0.17}_{- 0.03}^{+ 0.04}$ $\[-0.17_{-0.03}^{+0.04}\]$	$- {0.06}_{- 0.02}^{+ 0.02}$ $\[-0.06_{-0.02}^{+0.02}\]$
α_VO	Deviation from chemical equilibrium for VO	𝒩(0, 1)	$+ {0.30}_{- 0.03}^{+ 0.04}$ $\[+0.30_{-0.03}^{+0.04}\]$	$+ {0.42}_{- 0.02}^{+ 0.02}$ $\[+0.42_{-0.02}^{+0.02}\]$
α_FeH	Deviation from chemical equilibrium for FeH	𝒩(0, 1)	$+ {0.50}_{- 0.04}^{+ 0.04}$ $\[+0.50_{-0.04}^{+0.04}\]$	$+ {0.77}_{- 0.02}^{+ 0.02}$ $\[+0.77_{-0.02}^{+0.02}\]$
α_CrH	Deviation from chemical equilibrium for CrH	𝒩(0, 1)	$+ {0.01}_{- 0.10}^{+ 0.09}$ $\[+0.01_{-0.10}^{+0.09}\]$	$+ {0.23}_{- 0.07}^{+ 0.07}$ $\[+0.23_{-0.07}^{+0.07}\]$
α_NaH	Deviation from chemical equilibrium for NaH	𝒩(0, 1)	$+ {0.83}_{- 0.08}^{+ 0.08}$ $\[+0.83_{-0.08}^{+0.08}\]$	$+ {1.16}_{- 0.06}^{+ 0.05}$ $\[+1.16_{-0.06}^{+0.05}\]$
α_AlH	Deviation from chemical equilibrium for AlH	𝒩(0, 1)	$+ {0.01}_{- 0.31}^{+ 0.23}$ $\[+0.01_{-0.31}^{+0.23}\]$	$+ {0.43}_{- 0.06}^{+ 0.06}$ $\[+0.43_{-0.06}^{+0.06}\]$
α_HF	Deviation from chemical equilibrium for HF	𝒩(0, 1)	$+ {0.08}_{- 0.17}^{+ 0.16}$ $\[+0.08_{-0.17}^{+0.16}\]$	$- {0.14}_{- 0.13}^{+ 0.12}$ $\[-0.14_{-0.13}^{+0.12}\]$
α_HCl	Deviation from chemical equilibrium for HCl	𝒩(0, 1)	$- {0.19}_{- 0.08}^{+ 0.09}$ $\[-0.19_{-0.08}^{+0.09}\]$	$- {0.25}_{- 0.08}^{+ 0.07}$ $\[-0.25_{-0.08}^{+0.07}\]$
α_Na	Deviation from chemical equilibrium for Na	𝒩(0, 1)	$- {0.37}_{- 0.04}^{+ 0.04}$ $\[-0.37_{-0.04}^{+0.04}\]$	$- {0.17}_{- 0.03}^{+ 0.03}$ $\[-0.17_{-0.03}^{+0.03}\]$
α_Ca	Deviation from chemical equilibrium for Ca	𝒩(0, 1)	$+ {0.09}_{- 0.04}^{+ 0.05}$ $\[+0.09_{-0.04}^{+0.05}\]$	$+ {0.40}_{- 0.03}^{+ 0.02}$ $\[+0.40_{-0.03}^{+0.02}\]$
α_K	Deviation from chemical equilibrium for K	𝒩(0, 1)	$- {0.28}_{- 0.04}^{+ 0.04}$ $\[-0.28_{-0.04}^{+0.04}\]$	$- {0.04}_{- 0.03}^{+ 0.03}$ $\[-0.04_{-0.03}^{+0.03}\]$
α_Mg	Deviation from chemical equilibrium for Mg	𝒩(0, 1)	$- {0.23}_{- 0.45}^{+ 0.38}$ $\[-0.23_{-0.45}^{+0.38}\]$	$- {0.23}_{- 0.47}^{+ 0.40}$ $\[-0.23_{-0.47}^{+0.40}\]$
α_Al	Deviation from chemical equilibrium for Al	𝒩(0, 1)	$- {0.33}_{- 0.20}^{+ 0.18}$ $\[-0.33_{-0.20}^{+0.18}\]$	$+ {0.77}_{- 0.05}^{+ 0.04}$ $\[+0.77_{-0.05}^{+0.04}\]$
α_Fe	Deviation from chemical equilibrium for Fe	𝒩(0, 1)	$- {0.13}_{- 0.07}^{+ 0.07}$ $\[-0.13_{-0.07}^{+0.07}\]$	$+ {0.22}_{- 0.06}^{+ 0.05}$ $\[+0.22_{-0.06}^{+0.05}\]$
α_Ti	Deviation from chemical equilibrium for Ti	𝒩(0, 1)	$+ {0.03}_{- 0.08}^{+ 0.08}$ $\[+0.03_{-0.08}^{+0.08}\]$	$+ {0.21}_{- 0.05}^{+ 0.04}$ $\[+0.21_{-0.05}^{+0.04}\]$
log CH₄	Abundance of CH₄	𝒰(−14, -2)	$- {5.503}_{- 0.033}^{+ 0.036}$ $\[-5.503_{-0.033}^{+0.036}\]$	$- {5.369}_{- 0.022}^{+ 0.024}$ $\[-5.369_{-0.022}^{+0.024}\]$
log AlO	Abundance of AlO	𝒰(−14, -2)	$- {7.84}_{- 0.04}^{+ 0.04}$ $\[-7.84_{-0.04}^{+0.04}\]$	$- {7.65}_{- 0.05}^{+ 0.04}$ $\[-7.65_{-0.05}^{+0.04}\]$
log H⁻	Abundance of H⁻ bound-free opacity	𝒰(−12, -7)	$- {8.94}_{- 0.03}^{+ 0.04}$ $\[-8.94_{-0.03}^{+0.04}\]$	$- {8.78}_{- 0.02}^{+ 0.02}$ $\[-8.78_{-0.02}^{+0.02}\]$
log ¹²CO/¹³CO	Carbon isotope ratio ¹²C/¹³C in CO	𝒰(1.0, 3.0)	$+ {1.72}_{- 0.03}^{+ 0.03}$ $\[+1.72_{-0.03}^{+0.03}\]$	$+ {1.87}_{- 0.01}^{+ 0.01}$ $\[+1.87_{-0.01}^{+0.01}\]$
log C¹⁶O/C¹⁸O	Oxygen isotope ratio ¹⁶O/¹⁸O in CO	𝒰(1.5, 4.0)	$+ {2.63}_{- 0.04}^{+ 0.04}$ $\[+2.63_{-0.04}^{+0.04}\]$	$+ {2.84}_{- 0.03}^{+ 0.03}$ $\[+2.84_{-0.03}^{+0.03}\]$
log C¹⁶O/C¹⁷O	Oxygen isotope ratio ¹⁶O/¹⁷O in CO	𝒰(1.5, 4.0)	$+ {3.27}_{- 0.06}^{+ 0.06}$ $\[+3.27_{-0.06}^{+0.06}\]$	$+ {3.61}_{- 0.04}^{+ 0.04}$ $\[+3.61_{-0.04}^{+0.04}\]$
log $H_{2}^{16} O / H_{2}^{18} O$ $\[\mathrm{H}_2^{16} \mathrm{O} / \mathrm{H}_2^{18} \mathrm{O}\]$	Oxygen isotope ratio ¹⁶O/¹⁸O in H₂O	𝒰(1.5, 4.0)	$+ {2.81}_{- 0.05}^{+ 0.05}$ $\[+2.81_{-0.05}^{+0.05}\]$	$+ {2.83}_{- 0.03}^{+ 0.03}$ $\[+2.83_{-0.03}^{+0.03}\]$

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