{
  "abstract": "Ultra-long gamma-ray bursts (ul-GRBs) challenge standard collapsar models because their extreme durations require central engines active for $\\sim10^{3}-10^{4}$ s. While the prompt spectral evolution of typical GRBs is difficult to resolve due to their short durations, ul-GRBs provide a unique opportunity to study spectral evolution on extended timescales. We present a time-resolved spectroscopic study of GRB 220627A, one of the most luminous ul-GRBs known ($E_{\\rm iso}\\sim10^{54}$ erg, $T_{90}>1000$ s), consisting of two bright emission episodes separated by $\\sim600$ s quiescent interval. Using a novel HOP algorithm-based segmentation method, we identify optimal time intervals for time-resolved spectroscopy. A Comptonized power-law (CPL) model well describes the prompt emission ($\\sim 10$ keV-40 MeV) across all timescales. Fermi-GBM spectroscopy reveals a transition from a hard, slow-cooling synchrotron spectrum ($α_{\\rm I}=-0.70$) during episode-I to a softer, fast-cooling synchrotron spectrum ($α_{\\rm II}=-1.29$) during episode-II. This evolution closely resembles that of the magnetar-candidate GRB 091024A, highlighting a potential progenitor degeneracy based solely on spectral evolution. However, the extreme isotropic-equivalent energy exceeds the maximum energy available from magnetar spin-down, strongly favouring a blue supergiant (BSG) collapsar origin. The prolonged activity and multi-episode structure are naturally explained by sustained accretion through an extended stellar envelope. Our results demonstrate that ul-GRBs can display magnetar-like spectral evolution while being powered by BSG collapsars. GRB 220627A highlights the need for combining time-resolved spectroscopy with energetic constraints to distinguish between progenitor scenarios and understand the physical origin of ul-GRBs.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.02889",
  "author_total": 4,
  "authors": [
    {
      "name": "Ayush Garg"
    },
    {
      "name": "Amit Shukla"
    },
    {
      "name": "Dorottya Szécsi"
    },
    {
      "name": "G. C. Anupama"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6jzhxm898hjq7.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.02889",
  "fulltext_url": null,
  "id": "6jzhxm898hjq7",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.02889",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2610.02889",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6jzhxm898hjq7.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:45Z",
      "native_id": "2610.02889",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.02889"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Study of the Ultra-Long GRB 220627A: Exploring a Possible Blue Supergiant Collapsar Origin",
  "title_text": "Study of the Ultra-Long GRB 220627A: Exploring a Possible Blue Supergiant Collapsar Origin",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:45Z",
  "url": "https://research.draconitic.com/paper/6jzhxm898hjq7",
  "venue": "arXiv",
  "versions": []
}