{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"7bbc8f44d41062b587b011cd1bbfe749c5514ec8f53c42abdd4a0da367e79e41","created":"2026-10-03T07:17:54Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"8ad319e16af072df1a4297611f09dd3aad35b2e2f6242099d83fda1b45e250f8","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"astro.compact-binary-origins.lower-mass-gap","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Few compact objects have been found between about 2.5 and 5 solar masses, possibly because supernovae rarely make them.","posed_since":"1998","precise":"Determine whether the compact-object mass function has a real deficit between $\\sim 2.5$ and $\\sim 5\\,M_{\\mathrm{sun}}$, as X-ray binary samples suggest, or whether it is a selection effect, using gravitational-wave events (GW190814 secondary $\\sim 2.6\\,M_{\\mathrm{sun}}$, GW230529 primary $\\sim 2.5\\ \\text{to}\\ 4.5\\,M_{\\mathrm{sun}}$), microlensing and Gaia astrometric binaries. Answer: the depth of the gap as a rate-density ratio with credible interval.","problem_ref":null,"references":"","settled_by":"Population inference on gravitational-wave and astrometric samples with selection effects modeled, giving the rate density inside versus outside the gap.","status_note":"2024: GW230529 contained an object of $2.5\\ \\text{to}\\ 4.5\\ M_{\\mathrm{sun}}$ inside the putative gap, suggesting the gap is at most partly empty.","title":"Is there a gap between neutron star and black hole masses?","topic_ref":"daba472bb0b714510fff4a7bb5a67935cfcb27a99af5cf911b7cdf92f4674c82"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"e769b66bfd51463e09a5febf7de654f0cd6d504afe2677fbab7746494e4ddfed","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"8959060b3f7216c85144db5fe988994be597b4bc0ebe58f84cd13daa1ec8e1f0","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"eBNO-MhPreY9Ge8z-ISZ4B4XUA0off94LaW-X6WGZ_KvVMcVw5ZRNDN1imptEdp6sli7OpiFnEs7jhs97kgyBQ"},"schema":"pubphys.envelope/1"},"record_hash":"e769b66bfd51463e09a5febf7de654f0cd6d504afe2677fbab7746494e4ddfed","leaf_index":496}