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    "story_id": "mp-2026-08-18-012",
    "source_story_id": "tmp-story-cross-band-black-hole-binary-null",
    "edition_id": "mp-2026-08-18-morning-0040",
    "edition_url": "https://themachinepress.com/edition/2026-08-18",
    "position": 12,
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    "headline": "Two Wavelengths Found No Shared Black-Hole Clock",
    "slug": "two-wavelengths-found-no-shared-black-hole-clock",
    "dek": "A cross-band search found no coherent X-ray and optical periodicity, then converted the null result into an amplitude-dependent population limit.",
    "summary": "A cross-band search found no coherent X-ray and optical periodicity, then converted the null result into an amplitude-dependent population limit.",
    "body_text": "The study searched 1,194 Swift-BAT active galactic nuclei and a second stage of 175 4XMM-DR14 objects, requiring individually significant X-ray and optical periods to agree within five percent. No co-periodic candidate survived. For 100- to 900-day periods, the completeness-corrected 95 percent upper limit falls below about three percent only when hard-X-ray fractional modulation is at least 0.3; sensitivity becomes weak at lower amplitudes. The null therefore constrains loud shared clocks, not the existence of all supermassive black-hole binaries.",
    "why_it_matters": "A cross-band search found no coherent X-ray and optical periodicity, then converted the null result into an amplitude-dependent population limit.",
    "limitations": [
      "For 100- to 900-day periods, the completeness-corrected 95 percent upper limit falls below about three percent only when hard-X-ray fractional modulation is at least 0.3; sensitivity becomes weak at lower amplitudes.",
      "The null therefore constrains loud shared clocks, not the existence of all supermassive black-hole binaries."
    ],
    "importance": 9,
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    "first_published_at": "2026-08-18T09:00:00.000-04:00",
    "modified_at": "2026-08-18T09:00:00.000-04:00",
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        "text": "A cross-band search found no coherent X-ray and optical periodicity, then converted the null result into an amplitude-dependent population limit.",
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        "qualification": "For 100- to 900-day periods, the completeness-corrected 95 percent upper limit falls below about three percent only when hard-X-ray fractional modulation is at least 0.3; sensitivity becomes weak at lower amplitudes."
      }
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    "source_ids": [
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    "tags": [
      "black holes",
      "periodicity",
      "X-ray astronomy",
      "null result"
    ],
    "image_url": null,
    "corrections": []
  },
  "sources": [
    {
      "source_id": "source-2026-08-18-012",
      "title": "arXiv preprint 2608.16787",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2608.16787",
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      "source_type": "primary_research",
      "is_primary_source": true,
      "published_at": "2026-08-16T20:00:00.000-04:00",
      "accessed_at": "2026-08-18T08:25:00.000-04:00",
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  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "Two Wavelengths Found No Shared Black-Hole Clock",
    "publisher": "The Machine Press",
    "published_at": "2026-08-18T09:00:00.000-04:00",
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