{"work":{"id":"4f4acd67-8e97-47c0-aad7-86c8e42d560d","openalex_id":"https://openalex.org/W7080127275","doi":"10.48550/arxiv.2509.04151","arxiv_id":"2509.04151","raw_key":null,"title":"Evidence of the pair instability gap from black hole masses","authors":null,"authors_text":"Tong, Hui, Fishbach, Maya, Thrane, Eric, Mould, Matthew, Callister, Thomas A., Farah, Amanda, Guttman, Nir, Banagiri, Sharan, Beltran-Martinez, Daniel, Farr, Ben","year":2025,"venue":"astro-ph.HE","abstract":"Stellar theory predicts a forbidden range of black-hole masses between ${\\sim}50$--$130\\,M_\\odot$ due to pair-instability supernovae, but evidence for such a gap in the mass distribution from gravitational-wave astronomy has proved elusive. Early hints of a cutoff in black-hole masses at ${\\sim} 45\\,M_\\odot$ disappeared with the subsequent discovery of more massive binary black holes. Here, we report evidence of the pair-instability gap in LIGO--Virgo--KAGRA's fourth gravitational wave transient catalog (GWTC-4), with a lower boundary of $44_{-4}^{+5} M_\\odot$ (90\\% credibility). While the gap is not present in the distribution of \\textit{primary} masses $m_1$ (the bigger of the two black holes in a binary system), it appears unambiguously in the distribution of \\textit{secondary} masses $m_2$, where $m_2 \\leq m_1$. The location of the gap lines up well with a previously identified transition in the binary black-hole spin distribution; binaries with primary components in the gap tend to spin more rapidly than those below the gap. We interpret these findings as evidence for a subpopulation of hierarchical mergers: binaries where the primary component is the product of a previous black-hole merger and thus populates the gap. Our measurement of the location of the pair-instability gap constrains the $S$-factor for $^{12}\\rm{C}(\\alpha,\\gamma)^{16}\\rm{O}$ at 300keV to $260_{-108}^{+190}$ keV barns.","external_url":"https://arxiv.org/abs/2509.04151","cited_by_count":0,"metadata_source":"pith","metadata_fetched_at":"2026-08-05T02:28:24.338817+00:00","pith_arxiv_id":"2509.04151","created_at":"2026-05-08T23:14:23.262891+00:00","updated_at":"2026-08-05T02:49:54.815029+00:00","title_quality_ok":true,"display_title":"Evidence of the pair instability gap from black hole masses","render_title":"Evidence of the pair instability gap from black hole masses"},"hub":{"state":{"work_id":"4f4acd67-8e97-47c0-aad7-86c8e42d560d","tier":"hub","tier_reason":"10+ Pith inbound or 1,000+ external citations","pith_inbound_count":17,"external_cited_by_count":0,"distinct_field_count":5,"first_pith_cited_at":"2025-10-05T19:29:41+00:00","last_pith_cited_at":"2026-07-01T18:00:00+00:00","author_build_status":"not_needed","summary_status":"needed","contexts_status":"needed","graph_status":"needed","ask_index_status":"not_needed","reader_status":"not_needed","recognition_status":"not_needed","updated_at":"2026-08-23T06:19:56.799183+00:00","tier_text":"hub"},"tier":"hub","role_counts":[{"context_role":"background","n":7}],"polarity_counts":[{"context_polarity":"background","n":6},{"context_polarity":"support","n":1}],"runs":{},"summary":{},"graph":{},"authors":[]}}