On the Dynamics of Suddenly Heated Accretion Disks around Neutron Stars
Bibliographic record
Abstract
Type I X-ray bursts and superbursts on neutron stars release sudden and intense radiation fields into their surroundings. Here we consider the possible effects of these powerful explosions on the structure of the accretion disk. The goal is to account for the apparent evolution of the innermost regions of the accretion disk around 4U 1820-30 during a superburst. Three different processes are considered in detail: radiatively or thermally driven outflows, inflow due to Poynting-Robertson drag, and a structural change to the disk by X-ray heating. Radiatively driven winds with large column densities can be launched from the inner disk, but only for L / L Edd ≳ 1, which is expected to be obtained only at the onset of the burst. Furthermore, the predicted mass outflow rate is less than the accretion rate in 4U 1820-30. Estimates of the Poynting-Robertson or radiative drag timescale show that it is a very efficient means of removing angular momentum from the gas. However, the analytical results are likely only applicable at the innermost edge of the disk. X-ray heating gives a change in the disk scale height that is correlated with the blackbody temperature, as seen in the evolution during the 4U 1820-30 superburst. If this change in the scale height can alter the surface density, then the viscous time (with α ~ 0.03-0.2) is the closest match to the 4U 1820-30 results. We expect, however, that all three processes are likely ongoing when an accretion disk is subject to a sudden heating event. Ultimately, a numerical simulation of a disk around a bursting neutron star is required to determine the exact response of the disk. Magnetic truncation of the accretion flow is also considered and applied to the 4U 1820-30 X-ray reflection results.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".