{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"37c10969e1881f3e7d4c3cac9f2e7acfea814e04e90fd2e67ec03ba5d6651c29","created":"2026-10-03T07:17:55Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"b7e53cfea391534f9c8a8e62906dc47d83dfb5a0be5fced79ac26b1779b16c71","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"astro.smbh-binaries.individual-binary","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Several quasars brighten and dim periodically as if two black holes orbit each other, but none has been confirmed. A single proven close pair would anchor the whole population.","posed_since":"","precise":"Determine whether any electromagnetic candidate (periodic quasars, double-peaked or shifting broad lines, the blazar OJ 287) is a gravitationally bound binary with separation $< 1\\ \\mathrm{pc}$, or detect a continuous-wave pulsar timing source with an identified host galaxy. The answer is a confirmed system with measured orbital period and mass ratio.","problem_ref":null,"references":"","settled_by":"Coincident detection of a continuous-wave gravitational signal in pulsar timing data and a periodic electromagnetic counterpart at the same sky position and period.","status_note":"Candidates include OJ 287 and the radio blazar PKS 2131-021 (sinusoidal radio light curve, 2022); none is confirmed as of 2026.","title":"Is there any confirmed sub-parsec supermassive black hole binary?","topic_ref":"f9d7d39a2b73b71329d173a2c750a3256b1c03b685945ce091c4d937dee9943c"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"9e8fb02294e83dd82b6113fdc9bc9dae39fdbcc21cf0cb601a680958367824fa","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"ffe01841450ee2e4e4b6c993e2800c271e8290b01f86372e1a076ada474396df","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"sgZ4N2Jj5XLVHl6Z7IR6sJfv_KU576N25Xk3tRzuKgUeFv4qjnF1_OgeYv90byYs97CaYFy8zuFQzvQGeZLSBA"},"schema":"pubphys.envelope/1"},"record_hash":"9e8fb02294e83dd82b6113fdc9bc9dae39fdbcc21cf0cb601a680958367824fa","leaf_index":605}