THE CLUSTER AGES EXPERIMENT (CASE). III. ANALYSIS OF THE ECCENTRIC ECLIPSING BINARY V32 IN THE GLOBULAR CLUSTER NGC 6397
Bibliographic record
Abstract
We present spectroscopic and photometric observations of the eclipsing binary V32 located in the central field of the globular cluster NGC 6397. The variable is a single-line spectroscopic binary with an orbital period of 9.8783 days and a large eccentricity of e = 0.32. Its systemic velocity (γ = 20.7 km s −1 ) and metallicity ([Fe/H] ∼−1.9) are both consistent with cluster membership. The primary component of the binary is located at the top of the main-sequence turnoff on the cluster color–magnitude diagram. Only a shallow primary eclipse is observed in the light curve. Based on stellar models for an age of 12 Gyr and the mass function derived from the radial velocity curve, we estimate the masses to be M p = 0.79 M ☉ and M s = 0.23 M ☉ . The light curve of V32 can be reproduced by adopting R p = 1.569 R ☉ and R s = 0.236 R ☉ for the radii and i = 85.44 deg for the system inclination. The system geometry precludes observations of the secondary eclipse. The large eccentricity of the orbit is puzzling given that for metal-poor, halo binaries the transition from circular to eccentric orbit occurs at an orbital period of about 20 days. We suppose that the orbit of V32 was modified relatively recently by dynamical interaction with other cluster star(s). An alternative explanation of the observed eccentricity calls for the presence of a third body in the system.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.012 | 0.003 |
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".