The spin rates of O stars in WR+O Magellanic Cloud binaries
Bibliographic record
Abstract
ABSTRACT Some massive, merging black holes (BHs) may be descendants of binary O stars. The evolution and mass transfer between these O stars determine the spins of their progeny BH. These will be measurable with future gravitational wave detectors, incentivizing the measurement of the spins of O stars in binaries. We previously measured the spins of O stars in Galactic Wolf–Rayet (WR)+O binaries. Here we measure the ve sin i of four Large Magellanic Cloud (LMC) and two Small Magellanic Cloud (SMC) O stars in WR+O binaries to determine whether lower metallicity might affect the spin rates. We find that the O stars in Galactic and Magellanic WR+O binaries display average ve sin i = 258 ± 18 and 270 ± 15 km s−1, respectively. Two LMC O stars measured on successive nights show significant line width variability, possibly due to differing orbital phases exhibiting different parts of the O stars illuminated differently by their WR companions. Despite this variability, the ve sin i are highly supersynchronous but distinctly subcritical for the O stars in all these binaries; thus we conclude that an efficient mechanism for shedding angular momentum from O stars in WR+O binaries must exist. This mechanism, probably related to Roche lobe overflow (RLOF)-created dynamo magnetic fields, prevents nearly 100 per cent breakup spin rates, as expected when RLOF operates, as it must, in these stars. A Spruit–Tayler dynamo and O star wind might be that mechanism.
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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 | 0.000 |
| 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) | 0.001 | 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".