Hydrostatic Expansion and Spin Changes during Type I X‐Ray Bursts
Bibliographic record
Abstract
We present calculations of the spin-down of a neutron star atmosphere due to hydrostatic expansion during a type I X-ray burst. We show that Cumming & Bildsten incorrectly calculated the change in the moment of inertia of the atmosphere during a type I burst, resulting in a factor of 2 overestimation of the magnitude of the spin-down for rigidly rotating atmospheres. We derive the angular momentum conservation law in general relativity, both analytically for the case of slow rotation and numerically for rapidly rotating stars. We show that general relativity has a small effect on the angular momentum conservation law, at the level of 5%-10%. We show how to rescale our fiducial results to different neutron star masses, rotation rates, and equations of state and present some detailed rotational profiles. Comparing our results with recent observations of large frequency shifts in MXB 1658-298 and 4U 1916-053, we find that the spin-down expected if the atmosphere rotates rigidly is a factor of 2-3 less than the observed values. If differential rotation is allowed to persist, we find that the upper layers of the atmosphere do spin down by an amount comparable to or greater than the observed values. However, there is no compelling reason to expect the observed spin frequency to be that of only the outermost layers of the atmosphere. We conclude that hydrostatic expansion and angular momentum conservation alone cannot account for the largest frequency shifts observed during type I bursts.
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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 | 0.001 |
| 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) | 0.001 | 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".