Measurement of the Beta Decay of 26P to Determine Classical Nova 26Al Production in the Milky Way
Bibliographic record
Abstract
Observation across the Milky Way of a 1809-keV γ-ray characteristic of 26 Al decay provides direct evidence for ongoing nucleosynthetic production of 26 Al.Although massive stars and supernovae are likely to be the primary sites for 26 Al production, classical novae may also contribute a significant portion of the total amount of Galactic 26 Al.At peak nova temperatures of approximately 0.4 GK, the rate of the 25 Al(p,γ) 26 Si reaction, which bypasses 26 Al production and therefore places an upper limit on the amount of 26 Al contributed by novae to Galactic abundances, is likely dominated by a single 3 + resonance.Constraining the energy and strength of this resonance is therefore critical to determining the 25 Al(p,γ) 26 Si reaction rate.We have used a radioactive 26 P beam produced at the National Superconducting Cyclotron Laboratory to populate the 3 + state via beta decay, and have observed first evidence for its γ decay branch, the last piece of information needed to calculate the resonance strength.We find the 3 + state to have a resonance energy of E r = 414.9± 0.6 (stat) ± 0.3 (syst) ± 0.6 (lit.)keV and a resonance strength of ωγ = 23 ± 6 (stat) +11 -10 (lit.)meV.We have also used hydrodynamic nova simulations to model 26 Al production and we find that novae may contribute up to 0.6 solar masses of the Galactic 26 Al -38% of the total Galactic 26 Al abundance.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".