THE FACTORY AND THE BEEHIVE. II. ACTIVITY AND ROTATION IN PRAESEPE AND THE HYADES
Bibliographic record
Abstract
Open clusters are collections of stars with a single, well-determined age, and can be used to investigate the connections between angular-momentum evolution and magnetic activity over a star's lifetime. We present the results of a comparative study of the relationship between stellar rotation and activity in two benchmark open clusters: Praesepe and the Hyades. As they have the same age and roughly solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at approximate to 600 Myr. We have compiled a sample of 720 spectra-more than half of which are new observations-for 516 high-confidence members of Praesepe; we have also obtained 139 new spectra for 130 high-confidence Hyads. We have also collected rotation periods (P-rot) for 135 Praesepe members and 87 Hyads. To compare H alpha emission, an indicator of chromospheric activity, as a function of color, mass, and Rossby number R-o, we first calculate an expanded set of chi values, with which we can obtain the H alpha to bolometric luminosity ratio, L-H alpha/L-bol, even when spectra are not flux-calibrated and/or stars lack reliable distances. Our. values cover a broader range of stellar masses and colors (roughly equivalent to spectral types from K0 to M9), and exhibit better agreement between independent calculations, than existing values. Unlike previous authors, we find no difference between the two clusters in their H alpha equivalent width or L-H alpha/L-bol distributions, and therefore take the merged H alpha and Prot data to be representative of 600 Myr old stars. Our analysis shows that H alpha activity in these stars is saturated for R-o <= 0.11(-0.03)(+0.02) Above that value activity declines as a power-law with slope beta = -0.73(-0.12,)(+0.06) before dropping off rapidly at Ro approximate to 0.4. These data provide a useful anchor for calibrating the age-activity-rotation relation beyond 600 Myr.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 | 0.001 | 0.001 |
| 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 teacher head, 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".