{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"556511e642991ddba8a483913312d196b4fbb2118cc31a51eabd6b86ae05670e","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["521b3dba5c87b53a54fad45acca40c26c5295a657fb630e7f73d388349950319","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"53f7f2499bef8ea321b2551ccad7065dad621dc8e3c49085ac55f61f14ba6514","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":["ai:gpt-5.5"],"external_id":"astro.compact-binary-origins.pair-instability-gap","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Very massive stars should explode completely, because light in their cores turns into electron-positron pairs, leaving no black holes between roughly 50 and 130 solar masses; yet black holes in that range are seen merging.","posed_since":"","precise":"Pair-instability and pulsational pair-instability supernovae predict no black holes from single-star collapse between $M_{\\mathrm{low}} \\sim 45 \\text{ to } 65\\,M_{\\mathrm{sun}}$ and $M_{\\mathrm{high}} \\sim 120 \\text{ to } 130\\,M_{\\mathrm{sun}}$, with $M_{\\mathrm{low}}$ sensitive to the $12\\mathrm{C}(\\alpha,\\gamma)16\\mathrm{O}$ rate and rotation. Determine $M_{\\mathrm{low}}$ and whether gap events (GW190521; GW231123 with components $\\sim 100 \\text{ to } 140\\,M_{\\mathrm{sun}}$ and spins $\\sim 0.8 \\text{ to } 0.9$) are hierarchical mergers, stellar-merger products, or evidence of a higher gap edge. Answer: inferred $M_{\\mathrm{low}}$ and a classification of gap events.","problem_ref":"521b3dba5c87b53a54fad45acca40c26c5295a657fb630e7f73d388349950319","references":"","settled_by":"A population-level detection of the drop in the mass function together with spin signatures that separate hierarchical from first-generation black holes.","status_note":"2025: GW231123, with total mass about $190\\ \\text{to}\\ 265\\,M_{\\mathrm{sun}}$ and high spins, has components in or near the gap; analyses favor hierarchical mergers.","title":"Where is the lower edge of the pair-instability mass 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