JWST high-contrast spectroscopy with speckle modelling: Atmospheric retrievals of the T-dwarf companion HD 19467 B

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Volume 710 (June 2026)

A&A, 710 (2026) A293

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Table C.1

Retrieved parameters for HD 19467 B and 2M 0415.

Parameter	Prior	HD 19467 B	2M 0415
R [R_Jup]	[0.4, 1.2]	${0.790}_{- 0.013}^{+ 0.012}$ $Mathematical equation: $0.790_{ - 0.013}^{ + 0.012}$$	${0.846}_{- 0.005}^{+ 0.005}$ $Mathematical equation: $0.846_{ - 0.005}^{ + 0.005}$$
b (noise scaling)	[0, 2]	${0.194}_{- 0.007}^{+ 0.007}$ $Mathematical equation: $0.194_{ - 0.007}^{ + 0.007}$$	${0.450}_{- 0.005}^{+ 0.005}$ $Mathematical equation: $0.450_{ - 0.005}^{ + 0.005}$$
log g	[4, 6]	…	${4.97}_{- 0.08}^{+ 0.11}$ $Mathematical equation: $4.97_{ - 0.08}^{ + 0.11}$$
M [M_Jup]	𝒩(71.6, 5.0)	[66, 75]	…
v_rad,NRS1 [km/s]	[−100, 100]	${1.2}_{- 0.9}^{+ 0.9}$ $Mathematical equation: $1.2_{ - 0.9}^{ + 0.9}$$	${38.5}_{- 1.1}^{+ 1.2}$ $Mathematical equation: $38.5_{ - 1.1}^{ + 1.2}$$
v_rad,NRS2 [km/s]	[−100, 100]	${6.1}_{- 0.4}^{+ 0.5}$ $Mathematical equation: $6.1_{ - 0.4}^{ + 0.5}$$	${42.41}_{- 0.23}^{+ 0.22}$ $Mathematical equation: $42.41_{ - 0.23}^{ + 0.22}$$
T₀ [K]	[1000, 5000]	$2546_{- 194}^{+ 180}$ $Mathematical equation: $2546_{ - 194}^{ + 180}$$	$2308_{- 89}^{+ 85}$ $Mathematical equation: $2308_{ - 89}^{ + 85}$$
log P_RCE	[−2, 1]	$- {0.1}_{- 0.7}^{+ 0.2}$ $Mathematical equation: $ - 0.1_{ - 0.7}^{ + 0.2}$$	$- {0.55}_{- 0.16}^{+ 0.28}$ $Mathematical equation: $ - 0.55_{ - 0.16}^{ + 0.28}$$
∆ log P	[0.2, 1.8]	> 0.9 >	1.33
∇_T,0	[0, 0.42]	> 0.17	> 0.24
∇_T,1	[0, 0.42]	${0.29}_{- 0.05}^{+ 0.06}$ $Mathematical equation: $0.29_{ - 0.05}^{ + 0.06}$$	${0.372}_{- 0.018}^{+ 0.017}$ $Mathematical equation: $0.372_{ - 0.018}^{ + 0.017}$$
∇_T,2	[0, 0.42]	${0.267}_{- 0.024}^{+ 0.028}$ $Mathematical equation: $0.267_{ - 0.024}^{ + 0.028}$$	${0.248}_{- 0.009}^{+ 0.006}$ $Mathematical equation: $0.248_{ - 0.009}^{ + 0.006}$$
∇_T,3	[0, 0.42]	< 0.21	${0.251}_{- 0.008}^{+ 0.007}$ $Mathematical equation: $0.251_{ - 0.008}^{ + 0.007}$$
∇_T,4	[0, 0.42]	< 0.15	[0.11, 0.35]
∇_T,5	[0, 0.42]	[0.12, 0.37]	> 0.18
∇_T,6	[0, 0.42]	< 0.28	[0.10, 0.35]
$\log H_{2}^{16} O$ $Mathematical equation: $\log \,{\rm{H}}_2^{16}{\rm{O}}$$	[−12, −1]	$- {2.88}_{- 0.04}^{+ 0.05}$ $Mathematical equation: $ - 2.88_{ - 0.04}^{ + 0.05}$$	$- {2.90}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $ - 2.90_{ - 0.08}^{ + 0.09}$$
log ¹²CO	[−12, −1]	$- {3.88}_{- 0.05}^{+ 0.05}$ $Mathematical equation: $ - 3.88_{ - 0.05}^{ + 0.05}$$	$- {4.58}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $ - 4.58_{ - 0.08}^{ + 0.09}$$
log ¹²CH₄	[−12, −1]	$- {3.28}_{- 0.04}^{+ 0.04}$ $Mathematical equation: $ - 3.28_{ - 0.04}^{ + 0.04}$$	$- {3.17}_{- 0.08}^{+ 0.10}$ $Mathematical equation: $ - 3.17_{ - 0.08}^{ + 0.10}$$
log ¹²CO₂	[−12, −1]	$- {6.49}_{- 0.04}^{+ 0.04}$ $Mathematical equation: $ - 6.49_{ - 0.04}^{ + 0.04}$$	$- {7.22}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $ - 7.22_{ - 0.08}^{ + 0.09}$$
log ¹⁴NH₃	[−12, −1]	$- {5.05}_{- 0.08}^{+ 0.07}$ $Mathematical equation: $ - 5.05_{ - 0.08}^{ + 0.07}$$	$- {5.11}_{- 0.09}^{+ 0.11}$ $Mathematical equation: $ - 5.11_{ - 0.09}^{ + 0.11}$$
log H₂S	[−12, −1]	< −6.9	$- {4.51}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $ - 4.51_{ - 0.08}^{ + 0.09}$$
log PH₃	[−12, −1]	< −8.8	< −8.4
log SiO	[−12, −1]	$- {4.97}_{- 0.16}^{+ 0.14}$ $Mathematical equation: $ - 4.97_{ - 0.16}^{ + 0.14}$$	$- {5.73}_{- 0.29}^{+ 0.20}$ $Mathematical equation: $ - 5.73_{ - 0.29}^{ + 0.20}$$
log ¹²CO/¹³CO	[1, 3.4]	${2.18}_{- 0.05}^{+ 0.05}$ $Mathematical equation: $2.18_{ - 0.05}^{ + 0.05}$$	${1.930}_{- 0.025}^{+ 0.027}$ $Mathematical equation: $1.930_{ - 0.025}^{ + 0.027}$$
log ¹²CO/C¹⁸O	[1, 3.4]	${2.79}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $2.79_{ - 0.08}^{ + 0.09}$$	${2.67}_{- 0.05}^{+ 0.06}$ $Mathematical equation: $2.67_{ - 0.05}^{ + 0.06}$$
log ¹²CO/C¹⁷O	[1, 3.4]	> 3.20	> 3.18
$\log H_{2}^{16} O / H_{2}^{18} O$ $Mathematical equation: $\log {\mkern 1mu} {\rm{H}}_2^{16}{\rm{O}}/{\rm{H}}_2^{18}{\rm{O}}$$	[1, 3.4]	${2.68}_{- 0.13}^{+ 0.14}$ $Mathematical equation: $2.68_{ - 0.13}^{ + 0.14}$$	${2.74}_{- 0.06}^{+ 0.07}$ $Mathematical equation: $2.74_{ - 0.06}^{ + 0.07}$$
log ¹²CH₄/¹³CH₄	[1, 3.4]	${1.76}_{- 0.14}^{+ 0.19}$ $Mathematical equation: $1.76_{ - 0.14}^{ + 0.19}$$	${2.6}_{- 0.2}^{+ 0.3}$ $Mathematical equation: $2.6_{ - 0.2}^{ + 0.3}$$
log ¹²CH₄/CH₃D	[1, 3.4]	> 2.95	> 3.362
log ¹²CO₂/¹³CO₂	[1, 3.4]	> 2.2	${2.1}_{- 0.2}^{+ 0.4}$ $Mathematical equation: $2.1_{ - 0.2}^{ + 0.4}$$

Derived parameters

[C/H]	…	${0.14}_{- 0.04}^{+ 0.04}$ $Mathematical equation: $0.14_{ - 0.04}^{ + 0.04}$$	${0.15}_{- 0.07}^{+ 0.09}$ $Mathematical equation: $0.15_{ - 0.07}^{ + 0.09}$$
[O/H]	…	${0.18}_{- 0.04}^{+ 0.05}$ $Mathematical equation: $0.18_{ - 0.04}^{ + 0.05}$$	${0.11}_{- 0.08}^{+ 0.09}$ $Mathematical equation: $0.11_{ - 0.08}^{ + 0.09}$$
C/O	…	${0.389}_{- 0.012}^{+ 0.012}$ $Mathematical equation: $0.389_{ - 0.012}^{ + 0.012}$$	${0.451}_{- 0.006}^{+ 0.005}$ $Mathematical equation: $0.451_{ - 0.006}^{ + 0.005}$$
v_rad [km/s]	…	${3.7}_{- 0.5}^{+ 0.5}$ $Mathematical equation: $3.7_{ - 0.5}^{ + 0.5}$$	${40.4}_{- 0.5}^{+ 0.6}$ $Mathematical equation: $40.4_{ - 0.5}^{ + 0.6}$$
T_eff [K]	…	$1081_{- 29}^{+ 28}$ $Mathematical equation: $1081_{ - 29}^{ + 28}$$	$728_{- 8}^{+ 8}$ $Mathematical equation: $728_{ - 8}^{ + 8}$$
log(L/L_⊙)	…	$- {5.09}_{- 0.04}^{+ 0.03}$ $Mathematical equation: $ - 5.09_{ - 0.04}^{ + 0.03}$$	$- {5.719}_{- 0.018}^{+ 0.016}$ $Mathematical equation: $ - 5.719_{ - 0.018}^{ + 0.016}$$
log g	…	${5.45}_{- 0.03}^{+ 0.03}$ $Mathematical equation: $5.45_{ - 0.03}^{ + 0.03}$$	…

Notes. Notes. For HD 19467 B we adopt the dynamical mass as a Gaussian prior, (71.6, 5.0) M_Jup (Hoch et al. 2024), and derive log g from the retrieved radius and mass. For 2M 0415 log g is a free parameter and mass is derived. b is the noise scaling factor (lower values indicate a better fit). Derived parameters are computed from posterior samples of the free parameters, and uncertainties denote the corresponding posterior intervals. One-sided limits (< or >) indicate posteriors that rail against a prior boundary (prior-limited). Bracketed ranges indicate quantities that rail against both prior walls and are weakly constrained within the prior. The C/O and [O/H] represent bulk abundances, empirically corrected for oxygen condensation following Calamari et al. (2024). Elemental ratios [X/H] are logarithmic and Solar-normalised as described in Asplund et al. (2021).

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