Is the magnetic activity of Classical Cepheids modulated by pulsation? The case of eta Aquilae
Bibliographic record
Abstract
Classical Cepheids are evolved descendants of massive B stars with complex evolutionary histories. They exhibit large-amplitude radial pulsations, and their Period-Luminosity relation (Leavitt Law) makes them a foundational element in the Cosmic Distance Ladder and crucial to the recent increase in the significance of the "Hubble tension". In addition, it has been shown that Cepheids exhibit a number of intriguing phenomenon including infrared excess, cycle-to-cycle line variability, UV variability and phase-dependent X-ray "flashes". There are also open questions regarding the rotational history of Cepheids, mass loss through stellar winds and a discrepancy in stellar masses derived from evolution models versus pulsation calculations. Despite the cosmological and evolutionary importance of Cepheids, virtually nothing is known about their magnetic properties and what role magnetic fields may play in these observed phenomena. To date, the only Cepheid with a confirmed magnetic field detection is eta Aquilae. Here we present preliminary results of magnetic measurements from high-resolution spectropolarimetry of eta Aquilae across its 7.2 d pulsation cycle. The Least-Squares Deconvolution (LSD) Stokes V signatures exhibit an unusual shape across all phases which may be attributable to velocity gradients due to pulsation. We also discuss a newly proposed magnitude limited systematic survey of the brightest Galactic Cepheids. The aim of this survey is to provide the first characterization of magnetic fields across the Cepheid instability strip and identify suitable targets for follow-up phase-resolved spectropolarimetric 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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 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".