{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"9743aa88a9732402ca1d5e756dd9ab0de4622e91dea1af37fd7ee82a09ede589","created":"2026-10-03T07:17:55Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"d8dfd7f64e28548686859545f00e1eef937470da395ae53530162ec4e8e8840e","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"astro.sn-ia-progenitors.q-branch-delay","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Gaia found a group of heavy white dwarfs that stop cooling for billions of years, piling up in a narrow strip (the Q branch) of the color-brightness diagram. One proposed cause is that crystals rich in neon float upward and release energy, but whether this works in detail is not settled.","posed_since":"2019","precise":"About 6 percent of white dwarfs with $M \\sim 1.08 \\text{ to } 1.23\\,M_{\\mathrm{sun}}$ show an extra cooling delay of approximately 8 Gyr on the Q branch (Cheng, Cummings and Menard 2019). Determine whether 22Ne distillation (buoyant 22Ne-depleted crystals and gravitational energy release in a C/O/22Ne mixture) reproduces the delay length, the fraction of delayed stars and the mass range with a physically motivated 22Ne abundance, and identify which progenitors (single stars, mergers) have that composition.","problem_ref":null,"references":"","settled_by":"Cooling-model fits with distillation physics to the Gaia Q-branch kinematics and number counts, with a progenitor composition derived from merger or high-metallicity evolution models.","status_note":"Bedard et al. (Nature, 2024) showed distillation can halt cooling for billions of years if 22Ne is enhanced; a 2026 study found Q-branch merger remnants lack strong magnetism (Ould Rouis et al., ApJ, 2026).","title":"Does neon-22 distillation fully explain the Gaia white-dwarf Q branch 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