{
  "abstract": "In just over three years of operation, JWST has observed all seven planets of the TRAPPIST-1 system. The two innermost planets were found to have little to no atmosphere, barring the presence of high-altitude aerosols. Here we present the first JWST transit spectra of the habitable-zone exoplanet TRAPPIST-1 f, which were obtained with NIRISS SOSS over the course of five transits. At least one stellar flare occurred in each visit, but unlike observations of closer-in TRAPPIST-1 planets, no evidence for contamination of the transit spectra from unocculted stellar surface heterogeneities was found. This non-detection does not guarantee the absence of unocculted heterogeneities in all future transit observations of this planet, and it could be explained by the transit chord of TRAPPIST-1 f having properties similar to the average, out-of-transit, visible stellar hemisphere at the time of observation. The transit spectra exhibit slopes ranging from -365 ppm/um down to 15 ppm/um, which we attribute to stellar variability, that is, flares and/or smaller-scale events. The visits least affected by flares rule out H2/He-dominated atmospheres with surface pressures higher than about 20 mbar at 95% confidence. For high-mean-molecular-mass atmospheres, the exact upper limits on surface pressures depend on the reduction pipeline and on the treatment of the residual slopes in the transit spectra.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.17207",
  "author_total": 28,
  "authors": [
    {
      "name": "Olivia Lim"
    },
    {
      "name": "René Doyon"
    },
    {
      "name": "Ryan J. MacDonald"
    },
    {
      "name": "Étienne Artigau"
    },
    {
      "name": "Michael Radica"
    },
    {
      "name": "Mykhaylo Plotnykov"
    },
    {
      "name": "Alexandrine L'Heureux"
    },
    {
      "name": "Caroline Piaulet-Ghorayeb"
    },
    {
      "name": "Louis-Philippe Coulombe"
    },
    {
      "name": "David Lafrenière"
    },
    {
      "name": "Thomas J. Fauchez"
    },
    {
      "name": "Martin Turbet"
    },
    {
      "name": "Diana Valencia"
    },
    {
      "name": "Loïc Albert"
    },
    {
      "name": "Laura Flagg"
    },
    {
      "name": "Björn Benneke"
    },
    {
      "name": "Neil J. Cook"
    },
    {
      "name": "Pierre-Alexis Roy"
    },
    {
      "name": "Lisa Kaltenegger"
    },
    {
      "name": "Charles Cadieux"
    },
    {
      "name": "Nicolas B. Cowan"
    },
    {
      "name": "Michaël Gillon"
    },
    {
      "name": "Romain Allart"
    },
    {
      "name": "Lisa Dang"
    },
    {
      "name": "Doug Johnstone"
    },
    {
      "name": "Stefan Pelletier"
    },
    {
      "name": "Jared Splinter"
    },
    {
      "name": "Jake Taylor"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/czh167z7tcsq8.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.17207",
  "fulltext_url": null,
  "id": "czh167z7tcsq8",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.17207",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2608.17207",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-31",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/czh167z7tcsq8.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2608.17207",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.17207"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "Atmospheric Reconnaissance of TRAPPIST-1 f with JWST NIRISS SOSS: No Evidence for the Transit Light Source Effect",
  "title_text": "Atmospheric Reconnaissance of TRAPPIST-1 f with JWST NIRISS SOSS: No Evidence for the Transit Light Source Effect",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/czh167z7tcsq8",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-3881/ae990a",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}