{
  "abstract": "The James Webb Space Telescope (JWST) has uncovered a previously unexplored population of faint active galactic nuclei (AGNs) in the early Universe. We present MoM-BL-z10 at $z=9.9837\\pm0.0009$, identified through a systematic search for broad-line AGNs at $z\\geq6$ using public JWST/NIRSpec PRISM spectra from the DAWN JWST Archive. The PRISM spectrum exhibits a broad component in H$β$ at 5.35 microns. A narrow+broad Gaussian fit yields a broad H$β$ detection at S/N = 3.87, with FWHM = $3480^{+2040}_{-950}$ km s$^{-1}$ and $L_{{\\rm H}β,{\\rm broad}}=1.25^{+0.33}_{-0.31}\\times10^{42}$ erg s$^{-1}$. The detection of [Ne III] $\\lambda3870$ and the high [Ne III]/[O II] and [O III]/H$β$ ratios further support the AGN interpretation. Its rest-frame UV and optical continuum slopes, compact NIRCam morphology, and a tentative MIRI F770W detection suggest similarities to Little Red Dots (LRDs). The broad H$β$ detection enables the first virial SMBH mass estimate at $z\\sim10$. We derive $M_{\\rm BH}=3.6^{+5.8}_{-1.7}\\times10^7 M_\\odot$ and $λ_{\\rm Edd}=0.11^{+0.10}_{-0.07}$ using the standard single-epoch virial calibration and quasar bolometric correction. We also consider an alternative scenario adopting the LRD-specific bolometric correction and assuming $λ_{\\rm Edd}=1$, which yields $M_{\\rm BH}=2.1^{+0.6}_{-0.5}\\times10^6 M_\\odot$. Under either scenario, the inferred SMBH mass at a cosmic age of only 470 Myr highlights the challenge of rapid BH growth in the early Universe, suggesting super-Eddington accretion from a stellar-mass seed or a more massive seed. As the highest-redshift broad-line AGN identified to date, MoM-BL-z10 provides a new observational benchmark for understanding the early growth of supermassive black holes.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.28735",
  "author_total": 15,
  "authors": [
    {
      "name": "Xingyao Cai"
    },
    {
      "name": "Akio K. Inoue"
    },
    {
      "name": "Masafusa Onoue"
    },
    {
      "name": "Suzuka Arai"
    },
    {
      "name": "Yoshinobu Fudamoto"
    },
    {
      "name": "Rohan P. Naidu"
    },
    {
      "name": "Pascal A. Oesch"
    },
    {
      "name": "Jenny E. Greene"
    },
    {
      "name": "Ivo Labbe"
    },
    {
      "name": "Jorryt Matthee"
    },
    {
      "name": "Anna de Graaff"
    },
    {
      "name": "Yuma Sugahara"
    },
    {
      "name": "Ken Mawatari"
    },
    {
      "name": "Pratika Dayal"
    },
    {
      "name": "Xi Kang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2xm6s683f7mvn.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.28735",
  "fulltext_url": null,
  "id": "2xm6s683f7mvn",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.28735",
  "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"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7223219954",
  "pdf_url": "https://arxiv.org/pdf/2610.28735",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-20",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/2xm6s683f7mvn.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:19Z",
      "native_id": "2610.28735",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.28735"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Discovery of a Broad-Line Active Galactic Nucleus at $z = 9.98$",
  "title_text": "Discovery of a Broad-Line Active Galactic Nucleus at z = 9.98",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:19Z",
  "url": "https://research.draconitic.com/paper/2xm6s683f7mvn",
  "venue": "arXiv",
  "versions": []
}