{
  "abstract": "Granulation is a persistent feature of stars with outer convective layers and is the photospheric signature of near-surface convective energy transport. In disk-integrated observations, it produces stochastic brightness variations that contribute substantially to stellar variability on timescales of minutes to hours. High-precision, observations with JWST provide an opportunity to study the chromatic signatures of stellar granulation. This work aims to measure the amplitude and characteristic timescale of granulation-induced variability for solar-type stars and to investigate whether the granulation signal shows significant chromatic variation in the near-infrared. We accessed publicly available JWST/NIRISS SOSS time-series observations of LTT-9779 (G7V) and WASP-121 (F6V) and de-trended the light curves by fitting the transits, eclipses, and planetary phase curves. We computed power spectra from the de-trended light curves and fit them with a Harvey granulation profile. We first analyzed the broadband light curves to measure and fix the granulation timescale and then repeated the power-spectrum analysis in individual wavelength channels to measure the chromatic dependence of the granulation amplitude. For LTT-9779, we measure a broadband granulation amplitude of σ$=53.8^{+4.1}_{-4.0}$ppm at a timescale of τ$=4.8^{+1.5}_{-1.3}$min. For WASP-121, we measure σ$=59.3\\pm4.3$ppm and τ$=6.3^{+2.1}_{-1.8}$min. We also measure peak oscillation frequencies of ν$=3382^{+166}_{-191}μ$Hz and $1649^{+55}_{-69}μ$Hz in the bandpass-integrated power spectra of LTT-9779 and WASP-121, respectively. In the spectroscopic fits, we find $σ$ decreases with wavelength. Our results demonstrate a new observational window on short-timescale stellar variability and provides a way to characterize chromatic stellar noise in transit light curves.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.24550",
  "author_total": 12,
  "authors": [
    {
      "name": "William C. Waalkes"
    },
    {
      "name": "Nadiia Kostogryz"
    },
    {
      "name": "Valeriy Vasilyev"
    },
    {
      "name": "Rafael Luque"
    },
    {
      "name": "Alexander Shapiro"
    },
    {
      "name": "Jordi Blanco-Pozo"
    },
    {
      "name": "Ana Glidden"
    },
    {
      "name": "Jeff Valenti"
    },
    {
      "name": "Sami Solanki"
    },
    {
      "name": "Ignasi Ribas"
    },
    {
      "name": "Sara Seager"
    },
    {
      "name": "Laurent Gizon"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5nydcb8adystc.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.24550",
  "fulltext_url": null,
  "id": "5nydcb8adystc",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.24550",
  "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"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7223029681",
  "pdf_url": "https://arxiv.org/pdf/2610.24550",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-17",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5nydcb8adystc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:30:52Z",
      "native_id": "2610.24550",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.24550"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Granulation in Color: The Chromatic Stellar Flicker of LTT-9779 and WASP-121",
  "title_text": "Granulation in Color: The Chromatic Stellar Flicker of LTT-9779 and WASP-121",
  "type": "preprint",
  "updated_at": "2026-10-30T12:33:41Z",
  "url": "https://research.draconitic.com/paper/5nydcb8adystc",
  "venue": "arXiv",
  "versions": []
}