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  "story": {
    "story_id": "mp-2026-09-07-014",
    "source_story_id": "tmp-story-sn2023ufx-metal-poor-progenitor",
    "edition_id": "mp-2026-09-07-morning-0060",
    "edition_url": "https://themachinepress.com/edition/2026-09-07",
    "position": 14,
    "story_type": "dispatch",
    "section": "research",
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    "headline": "A Stripped Giant Left Three Oxygen Peaks",
    "slug": "a-stripped-giant-left-three-oxygen-peaks",
    "dek": "Late spectra of the very metal-poor supernova 2023ufx point to an asymmetric explosion, a 25-to-35-solar-mass progenitor and complex earlier mass loss.",
    "summary": "Late spectra of the very metal-poor supernova 2023ufx point to an asymmetric explosion, a 25-to-35-solar-mass progenitor and complex earlier mass loss.",
    "body_text": "A nebular spectrum taken about a year after explosion shows a triple-peaked oxygen line. Comparisons with models favor a zero-age main-sequence mass of roughly 25 to 35 Suns, while the low calcium-to-oxygen ratio supports a massive progenitor. Broad, boxy hydrogen emission and a flattening late light curve suggest material lost centuries to millennia before the blast. The authors conclude the event came from a heavily stripped red supergiant in a 2-to-7-percent-solar-metallicity environment; those inferences remain model-dependent.",
    "why_it_matters": "Late spectra of the very metal-poor supernova 2023ufx point to an asymmetric explosion, a 25-to-35-solar-mass progenitor and complex earlier mass loss.",
    "limitations": [
      "The authors conclude the event came from a heavily stripped red supergiant in a 2-to-7-percent-solar-metallicity environment; those inferences remain model-dependent."
    ],
    "importance": 8,
    "canonical_url": "https://themachinepress.com/story/mp-2026-09-07-014/a-stripped-giant-left-three-oxygen-peaks",
    "json_url": "https://themachinepress.com/story/mp-2026-09-07-014.json",
    "first_published_at": "2026-09-07T09:00:00.000-04:00",
    "modified_at": "2026-09-07T09:00:00.000-04:00",
    "content_status": "new",
    "is_carryover": false,
    "carryover_reason": null,
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        "claim_id": "claim-mp-2026-09-07-014-001",
        "text": "Late spectra of the very metal-poor supernova 2023ufx point to an asymmetric explosion, a 25-to-35-solar-mass progenitor and complex earlier mass loss.",
        "source_ids": [
          "source-2026-09-07-014"
        ],
        "qualification": "The authors conclude the event came from a heavily stripped red supergiant in a 2-to-7-percent-solar-metallicity environment; those inferences remain model-dependent."
      }
    ],
    "source_ids": [
      "source-2026-09-07-014"
    ],
    "tags": [
      "supernova",
      "stellar evolution",
      "metal-poor galaxy"
    ],
    "image_url": null,
    "corrections": []
  },
  "sources": [
    {
      "source_id": "source-2026-09-07-014",
      "title": "arXiv preprint 2609.04307",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2609.04307",
      "canonical_url": "https://arxiv.org/abs/2609.04307",
      "source_type": "primary_research",
      "is_primary_source": true,
      "published_at": "2026-09-03T14:00:00.000-04:00",
      "accessed_at": "2026-09-07T08:20:00.000-04:00",
      "supports_claim_ids": [
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  "corrections": [],
  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "A Stripped Giant Left Three Oxygen Peaks",
    "publisher": "The Machine Press",
    "published_at": "2026-09-07T09:00:00.000-04:00",
    "canonical_url": "https://themachinepress.com/story/mp-2026-09-07-014/a-stripped-giant-left-three-oxygen-peaks"
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