{
  "abstract": "We present shock breakout (SBO) modeling of the recently discovered X-ray transient EP260321a detected by the \\textit{Einstein Probe} mission. Our semi-analytic model, based on our previous work, follows the interaction between a supernova ejecta with a mildly relativistic outer envelope and a dense, wind-like circumstellar medium (CSM) by using a thin-shell approximation that incorporates relativistic effects. We find that the observed properties of the X-ray emission are well explained by the breakout emission powered by a high-velocity envelope with a kinetic energy of $\\sim3.5\\times10^{49}\\,\\mathrm{erg}$ (excluding the supernova ejecta) and a dense wind characterized by a mass-loss rate of $\\dot{M}\\simeq1.2\\times 10^{-3}(v_\\mathrm{w}/10^3\\,\\mathrm{km\\,s}^{-1})\\,M_\\odot\\,\\mathrm{yr}^{-1}$, where $v_\\mathrm{w}$ is the wind velocity. The observed burst duration requires the dense CSM to extend up to $\\sim350\\,R_\\odot$, corresponding to a CSM mass of $\\sim 10^{-5}\\,M_\\odot$. These results demonstrate that SBO observations provide a sensitive probe of mass loss from stripped-envelope supernova progenitors shortly before core collapse.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2607.24045",
  "author_total": 3,
  "authors": [
    {
      "name": "Akihiro Suzuki"
    },
    {
      "name": "Keiichi Maeda"
    },
    {
      "name": "Toshikazu Shigeyama"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8f3pw1v4vm6bq.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.24045",
  "fulltext_url": null,
  "id": "8f3pw1v4vm6bq",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.24045",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "openalex",
      "3103|Gamma-ray bursts and supernovae"
    ]
  ],
  "openalex": "W7171539338",
  "pdf_url": "https://arxiv.org/pdf/2607.24045",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8f3pw1v4vm6bq.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:37Z",
      "native_id": "2607.24045",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.24045"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Shock breakout from mildly relativistic ejecta in a dense wind: the case of EP260321a/SN 2026gzf",
  "title_text": "Shock breakout from mildly relativistic ejecta in a dense wind: the case of EP260321a/SN 2026gzf",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:37Z",
  "url": "https://research.draconitic.com/paper/8f3pw1v4vm6bq",
  "venue": "arXiv",
  "versions": []
}