{
  "abstract": "The radioactive isotope $^{44}$Ti in Cassiopeia A has been used as a tracer of the innermost ejecta and explosion asymmetries in core-collapse supernova explosions. However, recent stellar-evolution models suggest substantial $^{44}$Ti may also be synthesized prior to explosion during oxygen-carbon (O-C) shell mergers, a process proposed for the Cas A progenitor. We investigate this pre-supernova contribution by combining NuSTAR measurements of the spatial and kinematic distribution of $^{44}$Ti with X-ray and infrared ejecta diagnostics. The low- and intermediate-velocity $^{44}$Ti components are more closely associated with O-layer tracers than with shocked Fe-rich material. If the $^{44}$Ti associated with the O-layer tracers was synthesized prior to core collapse, it could contribute up to $\\sim7\\times10^{-5}~M_\\odot$, about half of the total. We find that this amount of $^{44}$Ti can be produced in O-C shell-merger models with ingestion rates and convective velocities higher than those in standard one-dimensional stellar-evolution calculations. Stable Fe-group abundance ratios measured with XRISM provide an additional constraint on the explosive contribution, as three-dimensional models with larger $^{44}$Ti yields tend to predict Ti/Fe and Mn/Cr ratios above the observed values. These results suggest that both pre-supernova shell-merger nucleosynthesis and explosive burning contribute to the observed $^{44}$Ti.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.16826",
  "author_total": 7,
  "authors": [
    {
      "name": "Toshiki Sato"
    },
    {
      "name": "Joshua Issa"
    },
    {
      "name": "Falk Herwig"
    },
    {
      "name": "Yui Kuboike"
    },
    {
      "name": "J. Martin Laming"
    },
    {
      "name": "Kai Matsunaga"
    },
    {
      "name": "Ryo Sawada"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aypqn3cyfysxd.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.16826",
  "fulltext_url": null,
  "id": "aypqn3cyfysxd",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.16826",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.16826",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/aypqn3cyfysxd.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:41Z",
      "native_id": "2609.16826",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.16826"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Testing a Pre-Supernova Contribution to $^{44}$Ti in Cassiopeia A",
  "title_text": "Testing a Pre-Supernova Contribution to ^44Ti in Cassiopeia A",
  "type": "preprint",
  "updated_at": "2026-10-30T12:21:41Z",
  "url": "https://research.draconitic.com/paper/aypqn3cyfysxd",
  "venue": "arXiv",
  "versions": []
}