Models for metal-poor stars with different initial abundances of C, N, O, Mg, and Si. II. Application to the colour–magnitude diagrams of the globular clusters 47 Tuc, NGC 6362, M 5, M 3, M 55, and M92
Bibliographic record
Abstract
ABSTRACT Stellar models for −2.5 ≤ [Fe/H] ≤−0.5 that have been computed for variations in the C:N:O abundance ratio (for two different values of [CNO/Fe]) are compared with HST Wide Field Camera 3 (WFC3) observations of the globular clusters (GCs) 47 Tuc, NGC 6362, M 5 M 3, M 55, and M 92. The bolometric corrections (BCs) used to transpose the models to the observed planes are based on new MARCS synthetic spectra that incorporate improved treatments of molecules that involve atoms of C, N, and O. On the assumption of well-supported distance moduli and reddenings, isochrones for [O/Fe] = 0.6 and [m/Fe] = 0.4 for the other α elements, which are favoured by binary stars in GCs, generally reproduce the main features of observed colour–magnitude diagrams (CMDs) to within ∼0.03 mag. In particular, they appear to match the spreads in the observed (MF336W − MF438W)0 colours that are spanned by CN-weak and CN-strong stars along the lower giant branch quite well, but not the bluest giants, which are suspected to be N-poor ([N/Fe] ≲ −0.5). Both the absolute (MF438W − MF606W)0 colours and the variations in these colours at a given MF606W magnitude on the giant branch are difficult to explain unless the reddest stars are C-rich ([C/Fe] ≳ +0.5). Allowing for moderate He abundance variations ($\delta \, Y \sim 0.05$) improves the fits to the observations.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".