{
  "abstract": "Faint Type I supernovae blur the boundaries between spectroscopic classes, obscuring their progenitors and explosion mechanisms. One proposed origin is a double detonation, in which ignition of an accreted helium shell triggers the explosion of a carbon oxygen white dwarf. Surviving helium is a direct prediction of this mechanism, but its strongest near-infrared feature overlaps with carbon and is ambiguous in isolation. Here we present SN 2024kce, observed with simultaneous optical and near-infrared spectroscopy eleven days before maximum light. We identify He I absorption at three wavelengths, all consistent with a velocity of 16,400 km/s, well above the photosphere. This is the first detection of helium before maximum light in a thermonuclear supernova. Helium at these velocities requires nearby radioactive material for non-thermal excitation, pointing to ash from a detonated surface helium shell. A double detonation model reproduces the optical spectral evolution, suppressed blue flux, and He I 1.083 micron absorption feature. SN 2024kce shares properties with both subluminous Type Ia supernovae and Ia-like calcium-rich transients, providing evidence that the same explosion mechanism operates across these classes. From early optical and near-infrared spectra to Rubin's First Look images, SN 2024kce showcases the full reach of modern observatories in exposing the physics of rare explosions.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.30674",
  "author_total": 29,
  "authors": [
    {
      "name": "Abigail Polin"
    },
    {
      "name": "Dillon Hasenour"
    },
    {
      "name": "Sahana Kumar"
    },
    {
      "name": "Willem Hoogendam"
    },
    {
      "name": "Jing Lu"
    },
    {
      "name": "Daniel Polin"
    },
    {
      "name": "Danielle Dickinson"
    },
    {
      "name": "Braden Garretson"
    },
    {
      "name": "Nidia Morrell"
    },
    {
      "name": "Huei Sears"
    },
    {
      "name": "Katie Auchettl"
    },
    {
      "name": "Teresa Boland"
    },
    {
      "name": "Christopher Burns"
    },
    {
      "name": "Kenneth C. Chambers"
    },
    {
      "name": "Dhvanil Desai"
    },
    {
      "name": "Jason T. Hinkle"
    },
    {
      "name": "Thressay Hoover"
    },
    {
      "name": "Eric Hsiao"
    },
    {
      "name": "Mark E. Huber"
    },
    {
      "name": "David O. Jones"
    },
    {
      "name": "Colin Macrie"
    },
    {
      "name": "Bailey Martin"
    },
    {
      "name": "Cameron Pfeffer"
    },
    {
      "name": "Miranda Pikus"
    },
    {
      "name": "Benjamin J. Shappee"
    },
    {
      "name": "Madeline Taylor"
    },
    {
      "name": "Brad E. Tucker"
    },
    {
      "name": "Michael Tucker"
    },
    {
      "name": "Huangfei Xiao"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cy55s3xv4h8ky.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.30674",
  "fulltext_url": null,
  "id": "cy55s3xv4h8ky",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.30674",
  "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.HE"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Gamma-ray bursts and supernovae"
    ]
  ],
  "openalex": "W7223359488",
  "pdf_url": "https://arxiv.org/pdf/2610.30674",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/cy55s3xv4h8ky.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:34Z",
      "native_id": "2610.30674",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.30674"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Early panchromatic spectra reveal helium in the thermonuclear supernova 2024kce",
  "title_text": "Early panchromatic spectra reveal helium in the thermonuclear supernova 2024kce",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:34Z",
  "url": "https://research.draconitic.com/paper/cy55s3xv4h8ky",
  "venue": "arXiv",
  "versions": []
}