{"paper":{"title":"Production of heavy $\\alpha$-elements and $^{44}$Ti in Cas A: comparison to abundances from 1D core-collapse supernova models and evidence for Carbon-Oxygen shell mergers","license":"http://creativecommons.org/licenses/by/4.0/","headline":"Carbon-oxygen shell mergers produce the high argon-to-neon ratios and part of the titanium-44 observed in Cassiopeia A.","cross_cats":["astro-ph.GA","astro-ph.SR"],"primary_cat":"astro-ph.HE","authors_text":"Chris L Fryer, Lorenzo Roberti, Luca Boccioli, Marco Pignatari, Samar Safi-Harb, Samuel Jones","submitted_at":"2026-03-25T19:29:58Z","abstract_excerpt":"The merger between the carbon (C) and oxygen (O) shells hours to days before the collapse of a massive star significantly changes its nucleosynthesis, which is reflected in the elemental ratios observed in supernova remnants (SNRs). We present a nucleosynthesis study of $^{44}$Ti production in core-collapse supernovae (CCSNe), highlighting large silicon (Si), sulfur (S), calcium (Ca), and, most importantly, argon (Ar) to neon (Ne) ratios as diagnostics for carbon-oxygen (C--O) shell mergers. We compare yields from eight different sets of CCSNe models to observations of Cassiopeia A (Cas A), an"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"C--O shell mergers are consistently the models that best match X-ray and infrared observations of Cas A, producing high Ar/Ne ratios (≳0.1) due to 20Ne depletion and production of 36Ar and 38Ar, with up to 20-30% of 44Ti located outside the reverse shock.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"That the 1D core-collapse supernova models used accurately capture the nucleosynthesis changes caused by C-O shell mergers without significant contributions from multidimensional effects or post-explosion mixing.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Core-collapse supernova models including C-O shell mergers best match observed elemental ratios in Cas A, indicating mergers occur and contribute up to 20-30% of 44Ti outside the reverse shock.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Carbon-oxygen shell mergers produce the high argon-to-neon ratios and part of the titanium-44 observed in Cassiopeia A.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"9dbf34f55f3cc43a1aadbe98746cd9ac33cdeec27306ced4bd2b9685aeeb979a"},"source":{"id":"2603.24758","kind":"arxiv","version":1},"verdict":{"id":"ac77eb81-645b-4978-9faf-8db0efa75f9a","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-19T17:34:52.603750Z","strongest_claim":"C--O shell mergers are consistently the models that best match X-ray and infrared observations of Cas A, producing high Ar/Ne ratios (≳0.1) due to 20Ne depletion and production of 36Ar and 38Ar, with up to 20-30% of 44Ti located outside the reverse shock.","one_line_summary":"Core-collapse supernova models including C-O shell mergers best match observed elemental ratios in Cas A, indicating mergers occur and contribute up to 20-30% of 44Ti outside the reverse shock.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"That the 1D core-collapse supernova models used accurately capture the nucleosynthesis changes caused by C-O shell mergers without significant contributions from multidimensional effects or post-explosion mixing.","pith_extraction_headline":"Carbon-oxygen shell mergers produce the high argon-to-neon ratios and part of the titanium-44 observed in Cassiopeia A."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2603.24758/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":63,"sample":[{"doi":"10.1093/mnras/stz2952","year":2020,"title":"2020, Monthly Notices of the Royal Astronomical Society, 491, 972, doi: 10.1093/mnras/stz2952","work_id":"1a665ece-19aa-417c-b810-1f201c52c42c","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.3847/1538-4357/ab64f8","year":2019,"title":"2019, The Astrophysical Journal, 890, 35, doi: 10.3847/1538-4357/ab64f8","work_id":"1a312d3f-9501-47bf-88da-9f14756b0f04","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1088/0004-637x/786/1/55","year":2014,"title":"G., Dwek, E., Kober, G., Rho, J., & Hwang, U","work_id":"b2ec0a5c-740d-4bc1-9a4f-c6acd4e0b05d","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1086/150157","year":1969,"title":"Arnett, W. D. 1969, The Astrophysical Journal, 157, 1369, doi: 10.1086/150157","work_id":"438d9893-19dd-4324-b4f2-dcf2aa6893c7","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1038/s41550-025-02714-4","year":2025,"title":"2025, Nature Astronomy, 10, 144, doi: 10.1038/s41550-025-02714-4","work_id":"6149038f-cb38-4861-abc7-08b763ab67fe","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":63,"snapshot_sha256":"dbfcb38545cb518b8815b10c014f8ed3280e42adcc5b984ee766358ca4a367c3","internal_anchors":2},"formal_canon":{"evidence_count":2,"snapshot_sha256":"9abaeeb651bf00e35e5b1a2e817747cca36f13071592b688a331ed0d5cb7e332"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}