Evidence for stellar contamination and water absorption in NGTS-5b’s transmission spectra with GTC/OSIRIS

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Table 3

Summary of Bayesian spectral retrieval statistics.

#	Model	dof^a	$χ_{MAP}^{2}^{b}$ $Mathematical equation: $\chi {_{{\rm{MAP}}}^2^b}$$	ln 𝒵	∆ ln 𝒵	DS
A. A flat-line model
i	Full model	139	346.1	752.88	0	–

B. A pure atmospheric model assuming equilibrium chemistry
i	Full model	133	305.6	790.34	0	–

C. A pure atmospheric model assuming free chemistry
i	Full model	120	298.2	792.21	0	–
ii	No Na	121	298.4	792.03	−0.17	N/A
iii	No K	121	297.9	793.21	1.00	−2.0σ
iv	No TiO	121	297.5	793.97	1.76	−2.4σ
v	No VO	121	298.7	794.08	1.87	−2.5σ
vi	No H₂O	121	304.1	789.40	−2.81	2.9σ
vii	No FeH	121	298.3	792.55	0.34	N/A

D. A pure stellar contamination model
i	Spots & faculae	130	300.6	780.06	0	–
ii	Only spots	134	297.9	784.51	4.45	−3.4σ
iii	Only faculae	134	345.0	769.74	−10.32	4.9σ

E. A hybrid model combining an atmosphere with equilibrium chemistry and stellar contamination
i	Full model	128	238.0	806.72	0	–

F. A hybrid model combining an atmosphere with free chemistry and stellar contamination
i	Full model	115	226.6	807.96	0	–
ii	No Na	116	227.4	809.65	1.69	−2.4σ
iii	No K	116	230.6	807.99	0.02	N/A
iv	No TiO	116	230.0	810.30	2.33	−2.7σ
v	No VO	116	226.7	810.69	2.72	−2.8σ
vi	No H₂O	116	240.6	802.05	−5.91	3.9σ
vii	No FeH	116	232.1	807.48	−0.49	N/A

Notes. ^(a)Degrees of freedom. ^(b)χ² for the maximum a posteriori (MAP) model.

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