{
  "abstract": "We report a hint of recurrent double-peaked $γ$-ray sub-flares in PKS~1424--418 during two similar major active epochs, MJD 56117--56498 and MJD 59669--59978. The candidate double-peaked sub-flares show a characteristic intra-subflare peak separation of $\\sim 11.8$ d and a neighbouring-subflare spacing of $\\sim 67$ d. Red-noise Monte Carlo tests indicate that the candidate recurrent double-peaked morphology is not easily reproduced by stochastic variability alone, with false-alarm probabilities of $p_{\\rm a}=0.0216$ and $p_{\\rm b}=0.0006$ for the two active epochs, respectively. In the simulations of the entire \\textit{Fermi} Large Area Telescope (LAT) light curve, no red-noise realisation reproduces both epoch-like structures. The spectral energy distribution (SED) modelling shows similar radiative properties for the two peaks of one double-peaked candidate, while changes in the Doppler factor appear to play an important role in the flaring activity. Together with the previously reported near-zero lag between the millimetre and $γ$-ray emission, these results suggest that the recurrent activity may be associated with the compact mm/sub-mm core region. We discuss a possible structured-jet scenario in which a single disturbance propagates through a chain of quasi-stationary recollimation shocks. In this picture, repeated interactions between the disturbance and the shock structure may qualitatively account for both the double-peaked sub-flare profiles and the observed $\\sim 11.8$ d and $\\sim 67$ d time-scales. Further active epochs are required to determine whether this similarity represents a recurrent long-term behaviour.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.28932",
  "author_total": 3,
  "authors": [
    {
      "name": "Na Wang"
    },
    {
      "name": "Tong Liu"
    },
    {
      "name": "Jingran Xu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bxmb6eb2tzmev.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.28932",
  "fulltext_url": null,
  "id": "bxmb6eb2tzmev",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.28932",
  "language": null,
  "licence": "CC0-1.0",
  "licence_label": "CC0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/publicdomain/zero/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.28932",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-24",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bxmb6eb2tzmev.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:24:11Z",
      "native_id": "2609.28932",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.28932"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Recurrent double-peaked $γ$-ray sub-flares in PKS 1424-418",
  "title_text": "Recurrent double-peaked γ-ray sub-flares in PKS 1424-418",
  "type": "preprint",
  "updated_at": "2026-10-30T12:24:11Z",
  "url": "https://research.draconitic.com/paper/bxmb6eb2tzmev",
  "venue": "arXiv",
  "versions": []
}