{
  "abstract": "Core-collapse supernova neutrinos offer a unique probe of physics beyond the Standard Model over Galactic baselines. Yet even a high-statistics nearby burst may be limited by source uncertainties, especially for propagation effects that average over energy and appear only as an overall flux suppression. Inspired by near--far comparisons in terrestrial oscillation experiments, we show that next-generation MeV observations of the supernova gamma-ray echo---the delayed 511 keV signal induced by the neutrino burst in the stellar envelope---can serve as an astrophysical near detector for the emitted $\\barν_e$ fluence. Comparing this echo-inferred source fluence with the surviving flux measured at Earth gives a direct test of neutrino propagation between the stellar surface and the detector. For pseudo-Dirac neutrinos, this turns the fully averaged active--sterile oscillation regime from an unobservable source-normalization ambiguity into a measurable near--far deficit, with sensitivity for nearby progenitors to splittings $δm^2\\gtrsim 10^{-18}~{\\rm eV}^2(0.22~{\\rm kpc}/D)(E_\\star/15~{\\rm MeV})$. The same near--far logic also applies to other propagation-induced modifications of the observed flux, including neutrino decay and neutrino interactions with Galactic dark matter.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.26908",
  "author_total": 2,
  "authors": [
    {
      "name": "Garv Chauhan"
    },
    {
      "name": "Yago Porto"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aba7cswjcpwcg.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.26908",
  "fulltext_url": null,
  "id": "aba7cswjcpwcg",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.26908",
  "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",
      "hep-ph"
    ],
    [
      "openalex",
      "3106|Neutrino Physics Research"
    ]
  ],
  "openalex": "W7214156387",
  "pdf_url": "https://arxiv.org/pdf/2609.26908",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/aba7cswjcpwcg.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:56Z",
      "native_id": "2609.26908",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.26908"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-ph",
      "subfield": "high-energy"
    }
  ],
  "title": "Supernova Gamma-Ray Echo as an Astrophysical Near Detector for Galactic Neutrino Propagation",
  "title_text": "Supernova Gamma-Ray Echo as an Astrophysical Near Detector for Galactic Neutrino Propagation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:56Z",
  "url": "https://research.draconitic.com/paper/aba7cswjcpwcg",
  "venue": "arXiv",
  "versions": []
}