On the Driving Mechanism and the Coexistence of Variable and Nonvariable Stars in the Domain of the Pulsating PG 1159 Stars
Bibliographic record
Abstract
We revisit the controversial question of the excitation of pulsation modes in models of PG 1159 stars that feature homogeneous envelopes with compositions comparable to those observed at the surface. We find, in agreement with some authors but contrary to others, that g -mode pulsations are naturally excited in such models and that there is no need to invoke composition gradients between the photosphere and the driving region in PG 1159 pulsators. We further find an excellent qualitative agreement between the range of predicted periods and the range of observed periods for all objects in our sample of pulsating stars, except for two models corresponding to the stars with the lowest surface gravities (central stars of planetary nebulae). We also address the problem of the coexistence of both variable and nonvariable PG 1159 stars in the same region of the log g - T eff diagram. We find a natural explanation for this cohabitation in terms of a dispersion in atmospheric parameters and in terms of a variation in surface composition from star to star. In particular, the most He-rich stars tend to be stable. We finally address the puzzling question of the existence of a correlation between pulsations and the presence of traces of nitrogen in the atmospheres of pulsating PG 1159 stars, a challenge that has remained unanswered so far.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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".