{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a259dde1d195403fdf804a9cfd4b6125758e4864576b502b6cf8695658bd1847","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","f23bf6d66ef21b310a438bb0f3be7060da5408602e867becf89834c08caa3fc7"],"salt":"15145b05a8fe085fe2236169dac02e7204f752d823501ee70eb4f92c0fc3e443","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"astro.sn-ia-progenitors.missing-companions","kind":"phenomenon","literature_status":"open","n":"2","parents":[],"plain":"If a white dwarf explodes while pulling gas from a normal star, that companion should survive and be seen near the center of the debris. Deep searches of young remnants have found no such star.","posed_since":"","precise":"Single-degenerate models predict a surviving donor at the center of young SN Ia remnants (for example Tycho, Kepler, SN 1006, SNR 0509-67.5), inflated and overluminous for $10^{3} \\text{ to } 10^{4}\\,\\mathrm{yr}$ and moving at a few hundred km/s; deep HST searches exclude such stars in several remnants. Explain the nondetections (double-degenerate origin, spin-up/spin-down delay that lets the donor shrink, or misidentified models), and reconcile the observed hypervelocity white dwarfs moving above $1000\\,\\mathrm{km/s}$ with the number expected if double detonations eject surviving companions.","problem_ref":"f23bf6d66ef21b310a438bb0f3be7060da5408602e867becf89834c08caa3fc7","references":"","settled_by":"A complete census of hypervelocity runaway white dwarfs from Gaia compared with the predicted ejection rate, together with deep companion limits in a larger set of Ia remnants.","status_note":"Hypervelocity runaway white dwarfs found in Gaia data since 2018 are candidate survivors of double detonations; whether their numbers match the SN Ia rate is debated.","title":"Why are surviving companion stars absent near Type Ia remnants?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"231daafcf9a99167fa5895cba0d754af253fc169cc2dd11ebf4c52b7976316b9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"bdac8915e3fdb55b7f14f8973517d720ca8542b151e5d271ca01d5708edfd27f","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"qmIgMcSF78AgJyXHzCQE9dJRCiJFz5YLGBIAHs5hF2MBHjnhg5tafV98DOS4kUNMJ88jwBjTrHNkxYHbcVzABg"},"schema":"pubphys.envelope/1"},"record_hash":"231daafcf9a99167fa5895cba0d754af253fc169cc2dd11ebf4c52b7976316b9","leaf_index":2422}