{
  "abstract": "We report the discovery of AT 2026abck, a young transient in a star-forming galaxy at $z=5.017\\pm0.001$, identified from Year-2 observations of the NEXUS JWST treasury program. AT 2026abck was detected on 2026 Aug 7 in NIRCam F200W imaging, with contemporaneous detection from parallel NIRCam F150W+F277W imaging. It brightened by $>1.4$ mag in F200W over $\\lesssim 12$ rest-frame days, as inferred from the last non-detection. AT 2026abck has nearly identical magnitudes of $\\sim27.4$ mag in F150W, F200W, and F277W, and is undetected in F444W ($>27.9$ mag, 3$σ$). It is the first robustly detected $z\\gtrsim 5$ transient in a non-lensing field. A blackbody fit yields a hot photosphere ($\\sim1.7\\times10^4\\, \\mathrm{K}$) with a radius of $\\sim7\\times10^{14}$ cm ($\\sim46$ au) and a bolometric luminosity of $\\sim3\\times10^{43}\\, {\\rm erg\\, s^{-1}}$. Its off-nucleus location and hot, UV-bright SED favor a core-collapse supernova origin, while its temperature and luminosity exceed those of normal SNe II at comparable early phases. We estimate that AT 2026abck was detected $\\sim4$-10 rest-frame days after explosion. The host is an intermediate-mass ($M_*\\approx10^{9.8}\\,M_\\odot$), star-forming (${\\rm SFR}\\approx20\\,M_\\odot\\,{\\rm yr^{-1}}$) galaxy on the $z\\approx5$ main sequence, $\\sim3.3$ dex more massive than the ultra-faint host of the lensed SN Eos at $z=5.13$. Together, the two events show that CCSNe at $z>5$ occur across a wide range of host environments, and AT 2026abck demonstrates that high-cadence blank-field JWST surveys can capture high-redshift SNe during their early, UV-bright phase.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.38373",
  "author_total": 11,
  "authors": [
    {
      "name": "Ming-Yang Zhuang"
    },
    {
      "name": "Yue Shen"
    },
    {
      "name": "Lei Hu"
    },
    {
      "name": "Justin D. R. Pierel"
    },
    {
      "name": "Zhiwei Pan"
    },
    {
      "name": "Zachary Stone"
    },
    {
      "name": "Adam J. Burgasser"
    },
    {
      "name": "Xiaohui Fan"
    },
    {
      "name": "Jenny E. Greene"
    },
    {
      "name": "Junyao Li"
    },
    {
      "name": "Feige Wang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7ptzgp3nbf05q.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.38373",
  "fulltext_url": null,
  "id": "7ptzgp3nbf05q",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.38373",
  "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.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "openalex",
      "3103|Gamma-ray bursts and supernovae"
    ]
  ],
  "openalex": "W7215096369",
  "pdf_url": "https://arxiv.org/pdf/2609.38373",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7ptzgp3nbf05q.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:48Z",
      "native_id": "2609.38373",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.38373"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "NEXUS: Discovery of a Luminous Young Transient at $z=5$",
  "title_text": "NEXUS: Discovery of a Luminous Young Transient at z=5",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:48Z",
  "url": "https://research.draconitic.com/paper/7ptzgp3nbf05q",
  "venue": "arXiv",
  "versions": []
}