{
  "abstract": "We report the discovery of extreme 37 GHz radio variability in early-stage active galactic nuclei (AGN). Most of these sources belong to the class of narrow-line Seyfert 1 (NLS1) galaxies, which harbour fast-growing, low-mass supermassive black holes that accrete at high Eddington ratios. At 37 GHz, these extraordinary AGN exhibit amplitude variability of three to four orders of magnitude over timescales of a few days. Notably, despite several attempts, we have not detected relativistic jets in these sources, suggesting that this phenomenon may occur very close to the black hole and may represent a new form of AGN variability. One of these sources, which flared at 37 GHz, was followed up with the Karl G. Jansky Very Large Array and Swift XRT/UVOT. Based on these observations, we estimated an e-folding timescale of mere hours, leading to variability brightness temperatures and variability Doppler factors that are extremely difficult to explain by an incoherent emitter. This suggests a possible detection of coherent emission from an AGN, although more observations will be needed to distinguish between alternative scenarios.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.16384",
  "author_total": 4,
  "authors": [
    {
      "name": "Emilia Järvelä"
    },
    {
      "name": "Patrizia Romano"
    },
    {
      "name": "Anne Lähteenmäki"
    },
    {
      "name": "Marco Berton"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3m36ekyrs1aq9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.16384",
  "fulltext_url": null,
  "id": "3m36ekyrs1aq9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.16384",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Astrophysical Phenomena and Observations"
    ]
  ],
  "openalex": "W7213406522",
  "pdf_url": "https://arxiv.org/pdf/2609.16384",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-14",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3m36ekyrs1aq9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:41Z",
      "native_id": "2609.16384",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.16384"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "NOCTURNE. II. Extreme radio variability in the heart of early-stage active galactic nuclei",
  "title_text": "NOCTURNE. II. Extreme radio variability in the heart of early-stage active galactic nuclei",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:41Z",
  "url": "https://research.draconitic.com/paper/3m36ekyrs1aq9",
  "venue": "arXiv",
  "versions": []
}