{
  "abstract": "Newly formed, rapidly rotating, strongly magnetized neutron stars (\"millisecond proto-magnetars\") are promising central engines for gamma-ray bursts (GRBs) and luminous supernovae. Although often modeled in isolation, they can be born surrounded by accretion disks in stellar collapse, neutron-star mergers, or accretion-induced collapse. We present axisymmetric GRMHD simulations of hyperaccretion onto such objects, including a physical equation of state and charged-current weak interactions. Holding the weakly magnetized accretion torus fixed, we vary the stellar dipole field strength to span crushed-magnetosphere, magnetically channeled accretion, and centrifugal-propeller regimes, and compare with an otherwise similar accreting black hole. Accretion compresses the stellar magnetosphere and opens additional magnetic flux, producing relativistic jet powers that exceed isolated-dipole spin-down estimates by factors of a few to ~10. Even while the magnetosphere remains compressed against the stellar surface, stronger fields increasingly impede accretion and enhance outflows. Channeled-accretion models show strong jet variability driven by plasmoid eruptions and intermittent magnetospheric accretion, whereas the propeller model produces a steadier, more powerful jet and rapid spin-down. The disk-magnetosphere interaction also regulates how efficiently the neutron star grows and whether it spins up or down; near spin equilibrium, inefficient accretion can delay collapse to a black hole relative to estimates based on the external mass-supply rate. Accreting proto-magnetars can therefore power relativistic jets and baryon-rich outflows with energetics comparable to those inferred for long GRBs and GRB-supernovae. A companion paper explores implications for neutron-rich ejecta and r-process nucleosynthesis.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.00174",
  "author_total": 6,
  "authors": [
    {
      "name": "Tejas Prasanna"
    },
    {
      "name": "Kyle Parfrey"
    },
    {
      "name": "Brian D. Metzger"
    },
    {
      "name": "Ore Gottlieb"
    },
    {
      "name": "Andrei Beloborodov"
    },
    {
      "name": "Koushik Chatterjee"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/29a6xz2x12hk5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.00174",
  "fulltext_url": null,
  "id": "29a6xz2x12hk5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.00174",
  "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",
      "astro-ph.HE"
    ],
    [
      "openalex",
      "3103|Gamma-ray bursts and supernovae"
    ]
  ],
  "openalex": "W7206173558",
  "pdf_url": "https://arxiv.org/pdf/2609.00174",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/29a6xz2x12hk5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2609.00174",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.00174"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic Explosions",
  "title_text": "GRMHD Simulations of Accreting Proto-Magnetars I. Implications for Gamma-Ray Burst Jets and Energetic Explosions",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/29a6xz2x12hk5",
  "venue": "arXiv",
  "versions": []
}