BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b

Alastair B Claringbold; Chloe E Fisher; James Kirk; Eva-Maria Ahrer; Anna B T Penzlin; Daniel P Thorngren; Mercedes López-Morales; Peter J Wheatley; Lili Alderson; Richard A Booth; Duncan A Christie; Charlotte Fairman; Nathan J Mayne; Mason McCormack; Annabella Meech; James E Owen; Vatsal Panwar; Denis E Sergeev; Daniel Valentine; Hannah R Wakeford; Maria Zamyatina

doi:10.1093/mnras/stag143

BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b

Alastair B Claringbold^*, Chloe E Fisher, James Kirk, Eva-Maria Ahrer, Anna B T Penzlin, Daniel P Thorngren, Mercedes López-Morales, Peter J Wheatley, Lili Alderson, Richard A Booth, Duncan A Christie, Charlotte Fairman, Nathan J Mayne, Mason McCormack, Annabella Meech, James E Owen, Vatsal Panwar, Denis E Sergeev, Daniel Valentine, Hannah R WakefordMaria Zamyatina

^*Corresponding author for this work

Research output: Contribution to journal › Article (Academic Journal) › peer-review

Abstract

We present the JWST NIRSpec/G395H transmission spectrum of the misaligned hot Jupiter HAT-P-30b from 2.8–5.2 um as part of the BOWIE-ALIGN survey, a comparative survey designed to probe the link between planet formation and atmospheric composition in samples of misaligned and aligned hot Jupiters orbiting F-type stars. Through independent data reductions and retrieval analyses, we find evidence for absorption features of H₂0 and C0₂ in the atmosphere of HAT-P-30 b. Our retrieved abundances are consistent with equilibrium chemistry, from which we infer a sub-solar C/O ratio (0.16–0.45), and sub-solar and sub-stellar metallicity (0.2–0.8solar, compared to a stellar metallicity of 1.1–1.6 x solar), with muted spectral features. This composition challenges formation models of continuous migration and accretion within a steady disc of stellar metallicity, and could be the result of low C/O ratio gas accretion within the water ice line, low metallicity accretion due to the trapping of volatiles further out in the disc, or the combined accretion of low metallicity gas and carbon-poor solids.

Original language	English
Article number	stag143
Number of pages	19
Journal	Monthly Notices of the Royal Astronomical Society
Volume	546
Issue number	4
Early online date	21 Jan 2026
DOIs	https://doi.org/10.1093/mnras/stag143
Publication status	Published - 1 Mar 2026

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Publisher Copyright:
© The Author(s) 2026.

Keywords

planets and satellites: composition
planets and satellites: atmospheres
techniques: spectroscopic
planets and satellites: gaseous planets

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Claringbold, A. B., Fisher, C. E., Kirk, J., Ahrer, E.-M., Penzlin, A. B. T., Thorngren, D. P., López-Morales, M., Wheatley, P. J., Alderson, L., Booth, R. A., Christie, D. A., Fairman, C., Mayne, N. J., McCormack, M., Meech, A., Owen, J. E., Panwar, V., Sergeev, D. E., Valentine, D., ... Zamyatina, M. (2026). BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b. Monthly Notices of the Royal Astronomical Society, 546(4), Article stag143. https://doi.org/10.1093/mnras/stag143

@article{fc695b7d0a9e46c2bcb98b69a5fa1cd2,

title = "BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b",

abstract = "We present the JWST NIRSpec/G395H transmission spectrum of the misaligned hot Jupiter HAT-P-30b from 2.8–5.2 um as part of the BOWIE-ALIGN survey, a comparative survey designed to probe the link between planet formation and atmospheric composition in samples of misaligned and aligned hot Jupiters orbiting F-type stars. Through independent data reductions and retrieval analyses, we find evidence for absorption features of H20 and C02 in the atmosphere of HAT-P-30 b. Our retrieved abundances are consistent with equilibrium chemistry, from which we infer a sub-solar C/O ratio (0.16–0.45), and sub-solar and sub-stellar metallicity (0.2–0.8solar, compared to a stellar metallicity of 1.1–1.6 x solar), with muted spectral features. This composition challenges formation models of continuous migration and accretion within a steady disc of stellar metallicity, and could be the result of low C/O ratio gas accretion within the water ice line, low metallicity accretion due to the trapping of volatiles further out in the disc, or the combined accretion of low metallicity gas and carbon-poor solids.",

keywords = "planets and satellites: composition, planets and satellites: atmospheres, techniques: spectroscopic, planets and satellites: gaseous planets",

author = "Claringbold, \{Alastair B\} and Fisher, \{Chloe E\} and James Kirk and Eva-Maria Ahrer and Penzlin, \{Anna B T\} and Thorngren, \{Daniel P\} and Mercedes L{\'o}pez-Morales and Wheatley, \{Peter J\} and Lili Alderson and Booth, \{Richard A\} and Christie, \{Duncan A\} and Charlotte Fairman and Mayne, \{Nathan J\} and Mason McCormack and Annabella Meech and Owen, \{James E\} and Vatsal Panwar and Sergeev, \{Denis E\} and Daniel Valentine and Wakeford, \{Hannah R\} and Maria Zamyatina",

note = "Publisher Copyright: {\textcopyright} The Author(s) 2026.",

year = "2026",

month = mar,

day = "1",

doi = "10.1093/mnras/stag143",

language = "English",

volume = "546",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

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Claringbold, AB, Fisher, CE, Kirk, J, Ahrer, E-M, Penzlin, ABT, Thorngren, DP, López-Morales, M, Wheatley, PJ, Alderson, L, Booth, RA, Christie, DA, Fairman, C, Mayne, NJ, McCormack, M, Meech, A, Owen, JE, Panwar, V, Sergeev, DE , Valentine, D , Wakeford, HR & Zamyatina, M 2026, 'BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b', Monthly Notices of the Royal Astronomical Society, vol. 546, no. 4, stag143. https://doi.org/10.1093/mnras/stag143

TY - JOUR

T1 - BOWIE-ALIGN

T2 - Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b

AU - Claringbold, Alastair B

AU - Fisher, Chloe E

AU - Kirk, James

AU - Ahrer, Eva-Maria

AU - Penzlin, Anna B T

AU - Thorngren, Daniel P

AU - López-Morales, Mercedes

AU - Wheatley, Peter J

AU - Alderson, Lili

AU - Booth, Richard A

AU - Christie, Duncan A

AU - Fairman, Charlotte

AU - Mayne, Nathan J

AU - McCormack, Mason

AU - Meech, Annabella

AU - Owen, James E

AU - Panwar, Vatsal

AU - Sergeev, Denis E

AU - Valentine, Daniel

AU - Wakeford, Hannah R

AU - Zamyatina, Maria

PY - 2026/3/1

Y1 - 2026/3/1

N2 - We present the JWST NIRSpec/G395H transmission spectrum of the misaligned hot Jupiter HAT-P-30b from 2.8–5.2 um as part of the BOWIE-ALIGN survey, a comparative survey designed to probe the link between planet formation and atmospheric composition in samples of misaligned and aligned hot Jupiters orbiting F-type stars. Through independent data reductions and retrieval analyses, we find evidence for absorption features of H20 and C02 in the atmosphere of HAT-P-30 b. Our retrieved abundances are consistent with equilibrium chemistry, from which we infer a sub-solar C/O ratio (0.16–0.45), and sub-solar and sub-stellar metallicity (0.2–0.8solar, compared to a stellar metallicity of 1.1–1.6 x solar), with muted spectral features. This composition challenges formation models of continuous migration and accretion within a steady disc of stellar metallicity, and could be the result of low C/O ratio gas accretion within the water ice line, low metallicity accretion due to the trapping of volatiles further out in the disc, or the combined accretion of low metallicity gas and carbon-poor solids.

AB - We present the JWST NIRSpec/G395H transmission spectrum of the misaligned hot Jupiter HAT-P-30b from 2.8–5.2 um as part of the BOWIE-ALIGN survey, a comparative survey designed to probe the link between planet formation and atmospheric composition in samples of misaligned and aligned hot Jupiters orbiting F-type stars. Through independent data reductions and retrieval analyses, we find evidence for absorption features of H20 and C02 in the atmosphere of HAT-P-30 b. Our retrieved abundances are consistent with equilibrium chemistry, from which we infer a sub-solar C/O ratio (0.16–0.45), and sub-solar and sub-stellar metallicity (0.2–0.8solar, compared to a stellar metallicity of 1.1–1.6 x solar), with muted spectral features. This composition challenges formation models of continuous migration and accretion within a steady disc of stellar metallicity, and could be the result of low C/O ratio gas accretion within the water ice line, low metallicity accretion due to the trapping of volatiles further out in the disc, or the combined accretion of low metallicity gas and carbon-poor solids.

KW - planets and satellites: composition

KW - planets and satellites: atmospheres

KW - techniques: spectroscopic

KW - planets and satellites: gaseous planets

U2 - 10.1093/mnras/stag143

DO - 10.1093/mnras/stag143

M3 - Article (Academic Journal)

SN - 0035-8711

VL - 546

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 4

M1 - stag143

ER -

BOWIE-ALIGN: Sub-solar C/O ratio and metallicity atmosphere of the misaligned hot Jupiter HAT-P-30 b

Abstract

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