Modelling spikes in quasar accretion disc temperature
Bibliographic record
Abstract
Microlensing observations indicate that quasar accretion discs have half-light radii larger than standard theories predict. The observations of Blackburne and colleagues suggest that these half-light radii may have a weak wavelength dependence. We consider disc temperature profiles that might match these observations. Nixon and colleagues have suggested that misaligned discs around spinning black holes can have annuli torn off them at radii where the Lense–Thirring torque overcomes the disc's viscosity. These annuli precess, spread radially, and intersect with the remaining disc, heating the disc at potentially large radii. However, unless the intersections occur at an angle of <1°, highly supersonic collisions will shock heat intersecting gas to T ∼ 107 K. Discs with such shock-heated regions have significantly larger half-light radii, but are overluminous in X-rays. If instead heating occurs through intermittent weak shocks, the X-ray luminosities are consistent with observations but the half-light radii are not significantly larger. We also study two phenomenological disc temperature profiles. Discs with a temperature spike at relatively large radii and lowered temperatures at radii inside the spike yield improved and acceptable fits to microlensing sizes in most cases. Such temperature profiles could in principle occur in sub-Keplerian discs partially supported by magnetic pressure. However, such discs overpredict the fluxes from quasars studied with microlensing except in the limit of negligible continuum emission from radii inside the temperature spike.
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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 | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| 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".