{
  "abstract": "We present the first direct comparison between accretion-disk (AD) and broad-line region (BLR) sizes in quasars at z > 2, combining continuum reverberation mapping with interferometric BLR constraints from GRAVITY and GRAVITY+. Using medium-band photometric monitoring with the MPG/ESO 2.2 m telescope, we measure inter-band continuum lags in SDSS J092034.17+065718.0 at z = 2.33 (J0920) and SMSS J052915.80-435152.0 at z = 3.96 (J0529), among the most luminous quasars known (Lbol ~ 10^48 erg s^-1). These are currently the only two quasars at z > 2 with spatially resolved BLRs and dynamical black-hole masses from interferometry. We detect significant continuum lags in both quasars, increasing monotonically with wavelength. The inferred UV disk sizes are RAD = 4.35 +0.78/-0.91 light-days for J0529 and RAD = 3.15 +0.50/-0.48 light-days for J0920. For J0920, accreting at lambda_Edd ~ 7-20, the disk size is consistent with standard thin-disk expectations despite its super-Eddington regime. For J0529, the disk size agrees with thin-disk predictions using the single-epoch black-hole mass, but implies disk inflation by a factor of a few if the GRAVITY+ dynamical mass, an order of magnitude lower, is adopted. UV continuum disk sizes therefore provide an independent physical scale constraining black-hole mass and accretion-rate models, particularly where BLR kinematics are dominated by outflows. The interferometric BLR sizes reveal pronounced radial hierarchies, with RBLR/RAD ~ 270 for J0529 (Hbeta) and ~115 for J0920 (Halpha). The successful lag detections at Lbol ~ 10^48 erg s^-1 show that continuum reverberation mapping remains feasible for the most luminous systems, opening a path to larger samples with surveys such as the Vera C. Rubin Observatory's LSST.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.00278",
  "author_total": 6,
  "authors": [
    {
      "name": "Francisco Pozo Nuñez"
    },
    {
      "name": "Eduardo Bañados"
    },
    {
      "name": "Swayamtrupta Panda"
    },
    {
      "name": "Amit Kumar Mandal"
    },
    {
      "name": "Bozena Czerny"
    },
    {
      "name": "Jochen Heidt"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5r7pdecxgxkjc.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.00278",
  "fulltext_url": null,
  "id": "5r7pdecxgxkjc",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.00278",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "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.GA"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.00278",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5r7pdecxgxkjc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:00Z",
      "native_id": "2609.00278",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.00278"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Accretion-disk sizes in two quasars with interferometrically resolved broad-line regions at $z=2.3$ and $z=4.0$",
  "title_text": "Accretion-disk sizes in two quasars with interferometrically resolved broad-line regions at z=2.3 and z=4.0",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:00Z",
  "url": "https://research.draconitic.com/paper/5r7pdecxgxkjc",
  "venue": "arXiv",
  "versions": []
}