{
  "abstract": "We investigate the stochastic X-ray variability of the changing-look active galactic nucleus 1ES 1927+654 during its 2018–2024 evolution, focusing on the recovery of the X-ray corona after its 2018 collapse. Using XMM-Newton EPIC-pn light curves in the 0.3–2.0 keV and 2.0–10.0 keV bands, we model the variability with Gaussian process (GP) covariance components including Matérn-3/2, damped random walk (DRW), stochastically driven damped simple harmonic oscillator (SHO), and white-noise terms. Bayesian model comparison reveals an X-ray stochastic-variability transition during the changing-look recovery phase. In the 2019 May 5 observation, the preferred covariance changes from a Matérn-3/2-like state to a DRW-like state within a single continuous exposure. A phenomenological gated-kernel estimate localizes this transition sharply in the hard band at t c ≃ 23.5 ks, while the soft band shows the same qualitative change over a broader interval. This transition occurs after the X-ray corona had reappeared but before the later pronounced hardening and brightening of the coronal emission, suggesting an early timing-domain signature of disk–corona reconfiguration. Phenomenologically, the dominant variability evolves from a smoother, finite-memory correlated process to a rougher, shorter-memory red-noise process. In the later 2022–2024 observations, SHO-like components associated with the known millihertz quasiperiodic oscillation (QPO) show increasing characteristic frequency and quality factor, indicating a faster and more coherent oscillatory component during the QPO-plus-jet phase. GP-based time-domain inference therefore provides a sensitive probe of stochastic-variability changes in recovering active galactic nucleus coronae.",
  "abstract_shown": true,
  "affiliations": [
    "Yunnan University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Lijuan Dong",
      "orcid": "0009-0008-0162-9771"
    },
    {
      "affs": [
        0
      ],
      "name": "Dahai Yan",
      "orcid": "0000-0003-4895-1406"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1c3pf0z1gra14.bib",
  "cited_by": 0,
  "doi": "10.3847/1538-4357/aeaa4e",
  "fulltext_url": null,
  "id": "1c3pf0z1gra14",
  "issns": [
    "1538-4357",
    "0004-637X"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aeaa4e",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "feed-journal",
      "astronomy/general"
    ],
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      "openalex",
      "3103|Astrophysical Phenomena and Observations"
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  "openalex": "W7168270516",
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aeaa4e/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-28",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/1c3pf0z1gra14.ris",
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      "first_seen": "2026-10-30T12:17:17Z",
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    {
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "journal-openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "Gaussian-process Evidence for a Stochastic-variability Transition in the Recovering Corona of 1ES 1927+654",
  "title_text": "Gaussian-process Evidence for a Stochastic-variability Transition in the Recovering Corona of 1ES 1927+654",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:11Z",
  "url": "https://research.draconitic.com/paper/1c3pf0z1gra14",
  "venue": "The Astrophysical Journal",
  "versions": []
}