{
  "abstract": "Context. Ultraluminous X-ray sources (ULXs) are thought to be powered, in many cases, by super-Eddington accretion onto compact objects. While soft X-ray lags have been detected in several ULXs, hard lags remain rare and poorly understood. Aims. We investigate the temporal and energy dependence of X-ray lags in NGC 7456 ULX-1 to constrain their physical origin and probe the super-Eddington accretion flow. Methods. We analyzed the two deepest XMM-Newton observations, taken in 2018 and 2023. Hard (1-10 keV) and soft (0.3-1 keV) light curves were cross-correlated using adaptive-binning techniques optimized for Poissonian low-count data. We measured lags over consecutive 10 ks intervals and investigated their energy dependence. Spectra were modeled using thermal and Comptonization models. Results. We detect significant hard X-ray lags in both observations, with the hard emission delayed by $\\sim 10^3$ s during phases of rapid flux variability. The delays are primarily driven by the lowest-energy photons. Spectral modeling indicates a Comptonization-dominated flow comprising a cooler, extended outer region and a hotter, compact inner flow embedded in an optically thick wind. We interpret the delays as the combined effect of inward propagation of accretion-rate fluctuations and photon diffusion within the dense outflow. Fluctuations first enhance the soft-emitting outer regions and then propagate toward the hotter inner flow, where photons undergo stronger Comptonization before escaping with a kilosecond delay. The small inferred inner emitting radius disfavors an intermediate-mass black hole accretor. Conclusions. The sign, amplitude, and energy dependence of the delays disfavor standard reverberation. Propagation-driven variability coupled with radiative transfer in optically thick winds appears to play a major role in shaping the timing properties of super-Eddington accretion flows.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Astronomy & Astrophysics, A97, 2026",
  "arxiv": "2610.01444",
  "author_total": 22,
  "authors": [
    {
      "name": "W. Leone"
    },
    {
      "name": "F. Pintore"
    },
    {
      "name": "C. Pinto"
    },
    {
      "name": "N. O. Pinciroli Vago"
    },
    {
      "name": "A. Sanna"
    },
    {
      "name": "A. Wolter"
    },
    {
      "name": "T. Di Salvo"
    },
    {
      "name": "R. Iaria"
    },
    {
      "name": "A. D'Aì"
    },
    {
      "name": "A. Anitra"
    },
    {
      "name": "R. Soria"
    },
    {
      "name": "P. Esposito"
    },
    {
      "name": "F. Barra"
    },
    {
      "name": "E. Ambrosi"
    },
    {
      "name": "S. Caserta"
    },
    {
      "name": "C. Salvaggio"
    },
    {
      "name": "R. Salvaterra"
    },
    {
      "name": "G. L. Israel"
    },
    {
      "name": "S. Banerjee"
    },
    {
      "name": "M. Marelli"
    },
    {
      "name": "G. Rodriguez-Castillo"
    },
    {
      "name": "L. Burderi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/dsckg2shb2c33.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.01444",
  "fulltext_url": null,
  "id": "dsckg2shb2c33",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.01444",
  "language": null,
  "licence": "CC-BY-SA-4.0",
  "licence_label": "CC BY-SA 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-sa/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.HE"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.01444",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/dsckg2shb2c33.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:03Z",
      "native_id": "2610.01444",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.01444"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Detection of kilosecond hard lags in the new pulsating ULX candidate NGC 7456 ULX-1",
  "title_text": "Detection of kilosecond hard lags in the new pulsating ULX candidate NGC 7456 ULX-1",
  "type": "preprint",
  "updated_at": "2026-11-05T15:20:56Z",
  "url": "https://research.draconitic.com/paper/dsckg2shb2c33",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1051/0004-6361/202661582",
      "pid": "3q2t7dp1xbzz9",
      "relation": "published-as",
      "title": "Detection of kilosecond hard lags in the new pulsating ULX candidate NGC 7456 ULX-1",
      "venue": "Astronomy & Astrophysics"
    }
  ]
}