{
  "abstract": "JWST has uncovered an abundant population of compact, red sources at high redshifts, termed little red dots (LRDs). We study whether they could be explained by thermally relaxed, hydrogen-burning, metal-enriched supermassive stars (SMSs). We construct 1D models in hydrostatic and thermal equilibrium, including a radiation-pressure-dominated, CNO-burning core and an outer envelope with metallicity-dependent opacity, non-adiabatic convection, and an effective treatment of super-Eddington surface layers. The luminosity is close to the Thomson-scattering Eddington limit. The Fe-opacity bump drives the formation of a strongly inflated, low-mass envelope, while hydrogen recombination terminates the envelope at a bound photosphere. For M=$10^4$ to $10^6$ Msun and metal mass fractions $Z=10^{-4}$ to $10^{-2}$, we find that the most metal-rich models (Z ~ $10^{-2}$) develop highly inflated envelopes and reach Teff ~ 7000 K. We suggest that such enriched SMSs could instead be assembled through runaway stellar collisions in compact star clusters. The GR instability sets a maximum mass that depends on the core rotation rate. The nonrotating and rotating models have maximum masses $3\\times10^5$ to $3\\times 10^6$ Msun, and maximum luminosity of the order $10^{44}$ erg/s, comparable to the observed bright-end cutoff of the LRD luminosity function. Core hydrogen depletion can drive initially stable SMSs across the instability threshold after a lifetime of order 1 Myr. If each LRD leaves a black hole retaining most of its mass, the observed LRD abundance implies a present-day remnant density of order $10^{-2}\\rm cMpc^{-3}$, consistent with the local abundance of supermassive black holes. Cool SMSs naturally produce weak X-ray and weak high-ionization lines. Non-LTE effects may significantly modify the Balmer features and the continuum opacity, and may lower Teff below our LTE value.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.22507",
  "author_total": 1,
  "authors": [
    {
      "name": "Wenbin Lu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bpgnf16jyv0jh.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.22507",
  "fulltext_url": null,
  "id": "bpgnf16jyv0jh",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.22507",
  "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"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7214012797",
  "pdf_url": "https://arxiv.org/pdf/2609.22507",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bpgnf16jyv0jh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2609.22507",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.22507"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Inflated Supermassive Stars as Little Red Dots and Progenitors of Supermassive Black Holes",
  "title_text": "Inflated Supermassive Stars as Little Red Dots and Progenitors of Supermassive Black Holes",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:19Z",
  "url": "https://research.draconitic.com/paper/bpgnf16jyv0jh",
  "venue": "arXiv",
  "versions": []
}