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Two Wavelengths Found No Shared Black-Hole Clock
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.
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.
Limits and context
- 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.
Key claims
A cross-band search found no coherent X-ray and optical periodicity, then converted the null result into an amplitude-dependent population limit.
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.
Evidence: source-2026-08-18-012
Sources
- arXiv preprint 2608.16787arXiv · primary research
Corrections
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