{
  "abstract": "Context . Young transiting exoplanets provide unique opportunities to probe planetary atmospheres during critical early phases of evolution when atmospheric escape and contraction are most active. HIP 67522 b, a 17 Myr old hot Jupiter with an extraordinarily low bulk density (<0.20 g cm −3 ), represents an ideal target for high-resolution transmission spectroscopy. Aims . We aim to constrain the mass and characterise the atmospheric composition, thermal structure, and dynamics of HIP 67522 b using ground-based high-resolution near-infrared spectroscopy with VLT/CRIRES+, complementing recent JWST observations. Methods . We obtained 92 high-resolution spectra ( R ≈ 10 5 ) with VLT/CRIRES+ in the K2166 band during a transit on 30 January 2025. We applied cross-correlation techniques and Bayesian nested sampling retrievals to constrain molecular abundances, temperature structure, and atmospheric dynamics. Results . We detected H 2 O at 20σ and CO at 5σ, confirming the extremely extended atmosphere of this low-mass giant. A velocity offset of −2.9 ± 0.2 km s −1 indicates day-to-night winds. The rotation velocity has been constrained to <1.8 km s −1 at 3σ, consistent with tidal locking. The retrieval analysis suggests a planetary mass of 27.7 −5.5 +5.9 Earth masses and statistically favours a two-temperature atmospheric structure with a discrete change at mbar pressures over an isothermal profile. This mass is twice as high as the mass estimated from JWST atmospheric observations and inconsistent at 3 σ , casting doubt on the actual planetary density of the planet. No matter the choice of atmospheric model, we derived a supersolar C/O ratio that is about 1.5 times solar, along with a supersolar metallicity that might further increase if the atmosphere is cloudy, which is a degeneracy that our data alone cannot resolve. We report a tentative 2 σ detection of HDO with an extreme enrichment factor of ∼1000 relative to the protosolar D/H ratio. If confirmed, this would be the first detection of deuterium in an exoplanet atmosphere and would require an intense escape rate to confirm its presence.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2602.03498",
  "author_total": 12,
  "authors": [
    {
      "name": "A. Lavail"
    },
    {
      "name": "F. Debras"
    },
    {
      "name": "B. Klein"
    },
    {
      "name": "E. Chabrol"
    },
    {
      "name": "S. Vinatier"
    },
    {
      "name": "T. Hood"
    },
    {
      "name": "A. Masson"
    },
    {
      "name": "J. Seidel"
    },
    {
      "name": "C. Moutou"
    },
    {
      "name": "S. Aigrain"
    },
    {
      "name": "A. Meech"
    },
    {
      "name": "O. Barragán"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/07hme7ntv18am.bib",
  "cited_by": 1,
  "doi": "10.1051/0004-6361/202659179",
  "fulltext_url": null,
  "id": "07hme7ntv18am",
  "issns": [
    "0004-6361",
    "1432-0746"
  ],
  "landing_url": "https://hal.science/hal-05843331v1",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "1.phys.astr"
    ],
    [
      "hal",
      "2.phys.astr.ep"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7159949231",
  "pdf_url": "https://hal.science/hal-05843331/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-06-02",
  "publisher": "EDP Sciences",
  "ris": "https://research.draconitic.com/paper/07hme7ntv18am.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:03Z",
      "native_id": "hal-05843331",
      "source": "hal",
      "url": "https://hal.science/hal-05843331v1"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "hal:2.phys.astr.ep",
      "subfield": "planetary"
    },
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "Atmospheric characterisation of HIP 67522 b with VLT/CRIRES+",
  "title_text": "Atmospheric characterisation of HIP 67522 b with VLT/CRIRES+",
  "type": "peer-reviewed",
  "updated_at": "2026-11-01T12:20:45Z",
  "url": "https://research.draconitic.com/paper/07hme7ntv18am",
  "venue": "Astronomy & Astrophysics - A&A",
  "versions": []
}