{
  "abstract": "Sulphur-bearing molecules have recently emerged as powerful tracers of atmospheric photochemistry in exoplanets observed with JWST. In several warm giant planets, SO$_2$ has been detected as a product of UV-driven chemical processing, suggesting a close connection between stellar irradiation, atmospheric metallicity, and sulphur chemistry. Whether these trends extend to Neptune-mass planets orbiting hotter stars remains largely unexplored. We investigate the atmospheric composition of the warm Neptune HD 106315 c, a Neptune-mass planet orbiting an F-type host star and subjected to a strong ultraviolet (UV) irradiation environment. Here, we report the low-resolution transmission spectrum between 5 and 12 $μ$m of HD 106315 c obtained with the MIRI Low-Resolution Spectrometer on-board JWST. Our work also includes re-analysis of archival data from HST WFC3 G141 mode of HD 106315 c, as well as contemporaneous XMM and Swift monitoring of the star in the UV and X-ray wavelength ranges. Together with the archival HST WFC3 data, we detect H$_2$O and find tentative evidence for NH$_3$, retrieving abundances of $\\log_{10}$(H$_2$O)$=-1.40^{+0.40}_{-0.74}$ and $\\log_{10}$(NH$_3$)$=-2.47^{+0.57}_{-0.89}$, together with an isothermal terminator temperature of $747^{+150}_{-155}$ K. We place stringent upper limits on CH$_4$, SO$_2$, and CS$_2$, finding no robust evidence for any sulphur-bearing species despite the intense irradiation received by the planet. The inferred water abundance implies a strongly metal-enriched atmosphere. Elevated intrinsic temperatures can reconcile the non-detections of CH$_4$ and CS$_2$ through carbon--sulphur coupling, while the absence of SO$_2$ points toward a reduced atmospheric sulphur inventory or a near-solar to mildly enhanced C/O ratio, and places HD 106315 c near the transition between sulphur-rich and sulphur-poor chemical regimes.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.09893",
  "author_total": 20,
  "authors": [
    {
      "name": "A. Dyrek"
    },
    {
      "name": "R. Waters"
    },
    {
      "name": "S. -M. Tsai"
    },
    {
      "name": "M. Holmberg"
    },
    {
      "name": "B. Edwards"
    },
    {
      "name": "J. Pye"
    },
    {
      "name": "M. Güdel"
    },
    {
      "name": "N. Crouzet"
    },
    {
      "name": "R. van Gompel"
    },
    {
      "name": "J. Polman"
    },
    {
      "name": "F. Ardevol Martinez"
    },
    {
      "name": "D. Barrado"
    },
    {
      "name": "W. De Gruijter"
    },
    {
      "name": "Th. Henning"
    },
    {
      "name": "S. Kendrew"
    },
    {
      "name": "N. Khorshid"
    },
    {
      "name": "Y. Miguel"
    },
    {
      "name": "M. Min"
    },
    {
      "name": "M. Morales-Calderon"
    },
    {
      "name": "M. Topinka"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4acvcdnzy5gea.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.09893",
  "fulltext_url": null,
  "id": "4acvcdnzy5gea",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.09893",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7212162962",
  "pdf_url": "https://arxiv.org/pdf/2609.09893",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-09",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/4acvcdnzy5gea.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:12Z",
      "native_id": "2609.09893",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.09893"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "JWST-SUPER I: New insights into irradiated warm Neptunes atmospheres from MIRI observations of HD 106315 c",
  "title_text": "JWST-SUPER I: New insights into irradiated warm Neptunes atmospheres from MIRI observations of HD 106315 c",
  "type": "preprint",
  "updated_at": "2026-10-30T12:20:12Z",
  "url": "https://research.draconitic.com/paper/4acvcdnzy5gea",
  "venue": "arXiv",
  "versions": []
}