{
  "abstract": "We report a day-scale hard lag between GeV and TeV $γ$-ray emission from the HBL 1ES~1959+650 in early 2024. Since the LHAASO-WCDA real-time monitoring system began operation in late 2023, multiple TeV flares from this source have been triggered, including the 1st trigger flare on 2024 February 9. A Bayesian-block analysis of the WCDA light curve identifies three TeV flares in 2024. For the second triggered flare, a discrete cross-correlation analysis reveals a $>3\\,σ$ correlation (relative to uncorrelated red-noise simulations) at a time delay of $Δt = 5.0_{-2.1}^{+2.1}$ days, with the TeV emission lagging the GeV. Time-resolved spectroscopy shows that this flare has the softest TeV spectrum among these flares (intrinsic spectral index $Γ=3.16\\pm0.18$), while the 1st trigger flare is harder ($Γ=2.48\\pm0.21$). The observed five-day hard lag is difficult to reconcile with a purely cooling-driven temporal ordering and is consistent with scenarios in which particle energization and/or transport may contribute to the evolution. However, the current data do not uniquely identify the underlying mechanism.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.02853",
  "author_total": 334,
  "authors": [
    {
      "name": "Zhen Cao"
    },
    {
      "name": "F Aharonian"
    },
    {
      "name": "Y.X Bai"
    },
    {
      "name": "Y.W Bao"
    },
    {
      "name": "D Bastieri"
    },
    {
      "name": "X.J Bi"
    },
    {
      "name": "Y.J Bi"
    },
    {
      "name": "W Bian"
    },
    {
      "name": "J Blunier"
    },
    {
      "name": "A.V Bukevich"
    },
    {
      "name": "C.M Cai"
    },
    {
      "name": "W.Y Cao"
    },
    {
      "name": "Zhe Cao"
    },
    {
      "name": "J Chang"
    },
    {
      "name": "J.F Chang"
    },
    {
      "name": "E.S Chen"
    },
    {
      "name": "G.H Chen"
    },
    {
      "name": "H.K Chen"
    },
    {
      "name": "L.F Chen"
    },
    {
      "name": "Liang Chen"
    },
    {
      "name": "Long Chen"
    },
    {
      "name": "M.J Chen"
    },
    {
      "name": "M.L Chen"
    },
    {
      "name": "Q.H Chen"
    },
    {
      "name": "S Chen"
    },
    {
      "name": "S.H Chen"
    },
    {
      "name": "S.Z Chen"
    },
    {
      "name": "T.L Chen"
    },
    {
      "name": "X.B Chen"
    },
    {
      "name": "X.J Chen"
    },
    {
      "name": "X.P Chen"
    },
    {
      "name": "Y Chen"
    },
    {
      "name": "N Cheng"
    },
    {
      "name": "Q.Y Cheng"
    },
    {
      "name": "Y.D Cheng"
    },
    {
      "name": "M.Y Cui"
    },
    {
      "name": "S.W Cui"
    },
    {
      "name": "X.H Cui"
    },
    {
      "name": "Y.D Cui"
    },
    {
      "name": "B.Z Dai"
    },
    {
      "name": "H.L Dai"
    },
    {
      "name": "L.X Dai"
    },
    {
      "name": "Z.G Dai"
    },
    {
      "name": "M Danzengluobu"
    },
    {
      "name": "Y.X Diao"
    },
    {
      "name": "A.J Dong"
    },
    {
      "name": "X.D Duan"
    },
    {
      "name": "J.H Fan"
    },
    {
      "name": "Y.Z Fan"
    },
    {
      "name": "J Fang"
    },
    {
      "name": "J.H Fang"
    },
    {
      "name": "K Fang"
    },
    {
      "name": "C.F Feng"
    },
    {
      "name": "H Feng"
    },
    {
      "name": "L Feng"
    },
    {
      "name": "S.H Feng"
    },
    {
      "name": "X.T Feng"
    },
    {
      "name": "Y Feng"
    },
    {
      "name": "Y.L Feng"
    },
    {
      "name": "S Gabici"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/90r0sxjejtrc3.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.02853",
  "fulltext_url": null,
  "id": "90r0sxjejtrc3",
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  "landing_url": "https://hal.science/hal-05759195v1",
  "language": "en",
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  "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"
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    [
      "hal",
      "0.phys"
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      "hal",
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      "openalex",
      "3106|Astrophysics and Cosmic Phenomena"
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  "openalex": "W7207789438",
  "pdf_url": "https://arxiv.org/pdf/2609.02853",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-02",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/90r0sxjejtrc3.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:37Z",
      "native_id": "hal-05759195",
      "source": "hal",
      "url": "https://hal.science/hal-05759195v1"
    },
    {
      "first_seen": "2026-10-30T12:18:16Z",
      "native_id": "2609.02853",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.02853"
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "LHAASO-WCDA observed a $\\sim$ 5 days TeV-delayed flaring event in blazar 1ES 1959+650",
  "title_text": "LHAASO-WCDA observed a ∼ 5 days TeV-delayed flaring event in blazar 1ES 1959+650",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:16Z",
  "url": "https://research.draconitic.com/paper/90r0sxjejtrc3",
  "venue": "HAL",
  "versions": []
}