{
  "abstract": "We consider a dilatonic dyon black hole solution with a gravitational radius of $2 μ$ and two charges, $Q_1$ (electric) and $Q_2$ (magnetic), within the framework of a four-dimensional gravitational model comprising one scalar field and one 2-form. The dilaton coupling constant $λ$ is fixed by $λ^2 = \\frac{3}{2}$. This solution is related to the $A_2$ Toda chain. The circular orbits of null geodesics are explored, and the fifth-order polynomial master equation governing the photon sphere radius $R_0$ is analyzed. It is shown to admit a unique solution satisfying $R_0 > 2 μ$. The circular null geodesics are proven to be unstable. Finally, the black hole shadow is examined, yielding relations for the shadow angle and the critical impact parameter.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: International Journal of Gravitation and Theoretical Physics, 2 (3), 1 (2026)",
  "arxiv": "2609.26421",
  "author_total": 2,
  "authors": [
    {
      "name": "Vladimir D. Ivashchuk"
    },
    {
      "name": "Evgeny E. Trubach"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3ad8rma6n534m.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.26421",
  "fulltext_url": null,
  "id": "3ad8rma6n534m",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.26421",
  "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",
      "gr-qc"
    ],
    [
      "arxiv",
      "hep-th"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.26421",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3ad8rma6n534m.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:39Z",
      "native_id": "2609.26421",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.26421"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    },
    {
      "field": "physics",
      "origin": "arxiv:hep-th",
      "subfield": "high-energy"
    }
  ],
  "title": "Photon sphere for a dyonic black hole corresponding to $A_2$ Toda chain",
  "title_text": "Photon sphere for a dyonic black hole corresponding to A_2 Toda chain",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:39Z",
  "url": "https://research.draconitic.com/paper/3ad8rma6n534m",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.53941/ijgtp.2026.100015",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}