{
  "abstract": "We present an exact solution in Freund–Nambu scalar–tensor gravity that extends the Janis–Newman–Winnicour (JNW) naked-singularity spacetime. The metric retains the JNW form governed by parameter n , while a new parameter q deforms the profile of the massive scalar field $$\\varphi .$$ φ . Test-particle dynamics incorporate a direct linear coupling $$g_s$$ g s to $$\\varphi .$$ φ . We compute the specific angular momentum, innermost stable circular orbit, and radiative efficiency, and derive epicyclic frequencies for quasi-periodic oscillations (QPOs). Within the epicyclic resonance model, the twin-peak QPO frequencies depend on n , q , and $$g_s.$$ g s . A Markov Chain Monte Carlo analysis of microquasars XTE J1550-564 and GRS 1915+105 yields black-hole masses $$M = 8.99 \\pm 0.55\\,M_\\odot $$ M = 8.99 ± 0.55 M ⊙ and $$13.3 \\pm 1.0\\,M_\\odot ,$$ 13.3 ± 1.0 M ⊙ , consistent with previous estimates, and gives the first observational constraints $$q \\approx 3,$$ q ≈ 3 , $$g_s \\approx 0.45.$$ g s ≈ 0.45 . These distinctive imprints demonstrate that this modified gravity framework provides a viable, testable arena for strong-field physics beyond general relativity.",
  "abstract_shown": true,
  "affiliations": [
    "Harbin Institute of Technology",
    "New Uzbekistan University",
    "University of Tashkent for Applied Sciences",
    "Central Asian University",
    "Khazar University",
    "Ulugh Beg Astronomical Institute",
    "National University of Uzbekistan",
    "Center for Fundamental Interactions and Astrophysics"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 6,
  "authors": [
    {
      "affs": [
        0,
        1,
        2
      ],
      "name": "Akbar Davlataliev"
    },
    {
      "affs": [
        3,
        4,
        5
      ],
      "name": "Bobur Turimov"
    },
    {
      "affs": [
        0,
        6,
        1
      ],
      "name": "Bobomurat Ahmedov"
    },
    {
      "affs": [
        7
      ],
      "name": "Yuri Vyblyi"
    },
    {
      "affs": [
        0
      ],
      "name": "Chengxun Yuan"
    },
    {
      "affs": [
        0
      ],
      "name": "Chen Zhou"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9en1tds886dt7.bib",
  "cited_by": 0,
  "doi": "10.1140/epjc/s10052-026-16324-5",
  "fulltext_url": "https://doi.org/10.1140/epjc/s10052-026-16324-5",
  "id": "9en1tds886dt7",
  "issns": [
    "1434-6044",
    "1434-6052"
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  "landing_url": "https://link.springer.com/article/10.1140/epjc/s10052-026-16324-5",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0",
  "metadata_licence": null,
  "native_subjects": [
    [
      "lcc",
      "QB460-466"
    ],
    [
      "lcc",
      "QC770-798"
    ],
    [
      "openalex",
      "3103|Astrophysical Phenomena and Observations"
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  "openalex": "W7222967350",
  "pdf_url": "https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16324-5.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-19",
  "publisher": "Springer Science and Business Media LLC",
  "ris": "https://research.draconitic.com/paper/9en1tds886dt7.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:04Z",
      "native_id": "10.1140/epjc/s10052-026-16324-5",
      "source": "crossref",
      "url": "https://link.springer.com/article/10.1140/epjc/s10052-026-16324-5"
    },
    {
      "first_seen": "2026-10-30T13:46:29Z",
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      "url": "https://doi.org/10.1140/epjc/s10052-026-16324-5"
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "lcc:QB460-466",
      "subfield": "general"
    },
    {
      "field": "physics",
      "origin": "issn:1434-6044",
      "subfield": "high-energy"
    },
    {
      "field": "physics",
      "origin": "lcc:QC770-798",
      "subfield": "nuclear"
    }
  ],
  "title": "Spherically symmetric vacuum solution in Freund–Nambu scalar–tensor gravity",
  "title_text": "Spherically symmetric vacuum solution in Freund–Nambu scalar–tensor gravity",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T13:46:29Z",
  "url": "https://research.draconitic.com/paper/9en1tds886dt7",
  "venue": "The European Physical Journal C",
  "versions": []
}