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    "story_id": "mp-2026-09-15-027",
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    "headline": "Two Black-Hole Binaries May Rise Above the Background",
    "slug": "two-black-hole-binaries-may-rise-above-the-background",
    "dek": "Population fits identify 3C 66B and Mrk 501 as promising individual gravitational-wave targets and forecast tens of SKAO detections.",
    "summary": "Population fits identify 3C 66B and Mrk 501 as promising individual gravitational-wave targets and forecast tens of SKAO detections.",
    "body_text": "A population model fitted to NANOGrav’s 15-year data asks whether electromagnetically identified supermassive-black-hole binaries occupy the rare loud tail of the gravitational-wave distribution. The analysis finds that 3C 66B and Mrk 501 are likely to stand out from the unresolved background, with 3C 66B robustly detectable in the authors’ Square Kilometre Array Observatory forecast. The same models predict tens of individually resolvable binaries and suggest their abundance could distinguish environmental hardening from purely gravitational-wave-driven evolution. These are model-based forecasts, not detections.",
    "why_it_matters": "Population fits identify 3C 66B and Mrk 501 as promising individual gravitational-wave targets and forecast tens of SKAO detections.",
    "limitations": [
      "These are model-based forecasts, not detections."
    ],
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    "first_published_at": "2026-09-15T09:00:00.000-04:00",
    "modified_at": "2026-09-15T09:00:00.000-04:00",
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        "text": "Population fits identify 3C 66B and Mrk 501 as promising individual gravitational-wave targets and forecast tens of SKAO detections.",
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        "qualification": "These are model-based forecasts, not detections."
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    "tags": [
      "supermassive black holes",
      "gravitational waves",
      "SKAO"
    ],
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  "sources": [
    {
      "source_id": "source-2026-09-15-016",
      "title": "arXiv preprint 2609.13363",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2609.13363",
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      "published_at": "2026-09-13T20:00:00.000-04:00",
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  "cite_this_report": {
    "title": "Two Black-Hole Binaries May Rise Above the Background",
    "publisher": "The Machine Press",
    "published_at": "2026-09-15T09:00:00.000-04:00",
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