{
  "abstract": "Population studies of fast radio burst (FRB) repetition typically model sources using a single distribution of steady, time-averaged burst rates, yet individual sources show significant departures from this assumption. Here we present FRB 20210601A, a source discovered by the Canadian Hydrogen Intensity Mapping Experiment FRB project (CHIME/FRB) that represents the most extreme such departure yet identified. The source produced at least nine bursts within a single 106.5 s interval -- the highest instantaneous burst rate yet reported from a repeating FRB source at $\\gtrsim 2$ Jy ms fluences -- yet remained otherwise undetected despite $\\sim 320$ hr of exposure spanning 7 yr. The active interval occurred while the source was in a side-lobe of the CHIME/FRB digitized beams, implying an instantaneous burst rate $\\gtrsim2.3\\times$ higher ($\\gtrsim$ 21 bursts) at main-lobe sensitivity. The source's intense, brief burst storm flanked by apparent quiescence despite substantial exposure is unique among the CHIME/FRB repeater sample, although its burst morphology, excess dispersion measure ($\\rm{DM_{excess}} \\sim 360$ pc cm$^{-3}$), Faraday rotation measure ($|\\rm{RM_{excess}}| \\sim 150-170$ rad m$^{-2}$), and temporal scattering ($τ\\lesssim 0.37$ ms at 600 MHz) are otherwise typical. Modeling a population of episodically active repeaters (i.e., short burst storms separated by long recurrence times) and accounting for declination-dependent exposure, we forecast $\\sim1-4$ additional source discoveries similar to FRB 20210601A over the next decade of CHIME/FRB operations, corresponding to a CHIME/FRB-detectable population of $9^{+200}_{-8}$ sources (68% credible interval). These results demonstrate that highly episodic repeaters could constitute a selection-biased but detectable component of the FRB population, possibly reflecting distinct magnetospheric states or triggering mechanisms.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.31365",
  "author_total": 32,
  "authors": [
    {
      "name": "Ryan Mckinven"
    },
    {
      "name": "Amanda M. Cook"
    },
    {
      "name": "Alice P. Curtin"
    },
    {
      "name": "B. M. Gaensler"
    },
    {
      "name": "Jason W. T. Hessels"
    },
    {
      "name": "Naman Jain"
    },
    {
      "name": "Lordrick Kahinga"
    },
    {
      "name": "Victoria M. Kaspi"
    },
    {
      "name": "Charanjot Brar"
    },
    {
      "name": "Tomas Cassanelli"
    },
    {
      "name": "Shami Chatterjee"
    },
    {
      "name": "Fengqiu Adam Dong"
    },
    {
      "name": "Maxwell Fine"
    },
    {
      "name": "Emmanuel Fonseca"
    },
    {
      "name": "Afrokk Khan"
    },
    {
      "name": "Bikash Kharel"
    },
    {
      "name": "Calvin Leung"
    },
    {
      "name": "Robert Main"
    },
    {
      "name": "Kiyoshi W. Masui"
    },
    {
      "name": "Kyle McGregor"
    },
    {
      "name": "Nicole Mulyk"
    },
    {
      "name": "Mason Ng"
    },
    {
      "name": "Kenzie Nimmo"
    },
    {
      "name": "Ayush Pandhi"
    },
    {
      "name": "Aaron B. Pearlman"
    },
    {
      "name": "Ziggy Pleunis"
    },
    {
      "name": "Mawson W. Sammons"
    },
    {
      "name": "Paul Scholz"
    },
    {
      "name": "Kaitlyn Shin"
    },
    {
      "name": "Seth R. Siegel"
    },
    {
      "name": "Kendrick Smith"
    },
    {
      "name": "Ingrid Stairs"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/02h9j5am3ver0.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.31365",
  "fulltext_url": null,
  "id": "02h9j5am3ver0",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.31365",
  "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|Pulsars and Gravitational Waves Research"
    ]
  ],
  "openalex": "W7223265292",
  "pdf_url": "https://arxiv.org/pdf/2610.31365",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/02h9j5am3ver0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:34Z",
      "native_id": "2610.31365",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.31365"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "FRB 20210601A: Extreme Temporal Clustering in a Repeating Fast Radio Burst Source as Evidence for a Hidden Class of Episodic Repeaters",
  "title_text": "FRB 20210601A: Extreme Temporal Clustering in a Repeating Fast Radio Burst Source as Evidence for a Hidden Class of Episodic Repeaters",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:34Z",
  "url": "https://research.draconitic.com/paper/02h9j5am3ver0",
  "venue": "arXiv",
  "versions": []
}