Detection of<i>p</i>‐Mode Pulsations and Possible Ellipsoidal Luminosity Variations in the Hot Subdwarf B Star KPD 1930+2752
Bibliographic record
Abstract
We report the discovery of multiperiodic luminosity variations in the hot B subdwarf KPD 1930+2752. This star was selected as a potential target in the course of our ongoing survey to search for pulsators of the EC 14026 type. Our model atmosphere analysis of the time-averaged optical spectrum of KPD 1930+2752 indicates that this star has T eff ≃ 33,280 K and log g ≃ 5.61, which places it well within the theoretical EC 14026 instability strip. At least 44 harmonic oscillations are seen in the light curve, with periods in the range 145-332 s, and amplitudes in the range 0.064%-0.451% of the mean brightness of the star. In addition, the light curve is dominated by a nearly sinusoidal variation with a period of ~4108.9 s and amplitude of ~1.39%. This latter variation is unique among the known EC 14026 stars. We argue that this relatively slow luminosity variation is likely due to the ellipsoidal deformation of the sdB star in a close binary system containing a faint invisible companion (possibly a white dwarf). Using a new period-matching technique based on a genetic algorithm, we demonstrate that the dense observed period spectrum in the 145-332 s interval is compatible with a theoretical low-degree p -mode spectrum that is rotationally split in a star rotating with a period of ~8217.8 s, the value expected from the ellipsoidal effect invoked to explain the observed long-period variation. This interpretation awaits the test of time-resolved spectroscopy. If confirmed, the potential of KPD 1930+2752 as a laboratory for EC 14026 seismology will become immense.
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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 | 0.000 |
| 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) | 0.000 | 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".