{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"82b1181f4bb28b5e8de51175a1f49a31a3d892870bb7789f4c241ee1f5caebef","created":"2026-10-03T07:17:54Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"4028a2f39ea665b6dff6fbaf2c80b91e4851a18e32895eda61f49468c5365219","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"astro.compact-binary-origins.spin-discrepancy","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Black holes feeding on companion stars appear to spin near the maximum rate, while most black holes seen merging barely spin.","posed_since":"","precise":"X-ray continuum-fitting and reflection methods give spins $a* > \\sim 0.8$ for many black holes in X-ray binaries, while gravitational-wave populations show $\\chi_{\\mathrm{eff}}$ concentrated near $\\sim 0.05$ with small component spins. Determine whether this reflects different formation histories (spin-up by accretion or tidal locking versus slow birth spins from efficient core-envelope coupling), systematic errors in X-ray methods, or gravitational-wave prior choices. Answer: a model consistent with both populations or a demonstrated systematic error.","problem_ref":null,"references":"","settled_by":"Independent spin measurements of X-ray binary black holes (for example X-ray polarimetry or quasi-periodic oscillations) agreeing or disagreeing with spectral methods, and prior-robust gravitational-wave spin distributions.","status_note":"","title":"Why do X-ray binary black holes spin fast, merging ones slowly?","topic_ref":"daba472bb0b714510fff4a7bb5a67935cfcb27a99af5cf911b7cdf92f4674c82"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"12a6a441553e05df53a2ec73d516876c613301605cde8dec5442e6b9046f15d9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"267dbabe4f5b45ae2dc71fb15b20d084c9b63dc1a524426c082c5f5137b28f8d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"2U44eJ0DVh4fff09sc2n7si_FeVZJi5hv7pHd_qa_3R2DQ8YTkl6iT691UznheuZ_1lQ8MDLK4AmIbrlffQaBA"},"schema":"pubphys.envelope/1"},"record_hash":"12a6a441553e05df53a2ec73d516876c613301605cde8dec5442e6b9046f15d9","leaf_index":499}