Dramatic X-ray spectral variability of a Compton-thick type-1 QSO at z similar to 1
Bibliographic record
Abstract
We report on the discovery of a dramatic X-ray spectral variability event observed in a z ∼ 1 broad line type-1 QSO.The XMM-Newton spectrum from the year 2000 is characterized by an unobscured power-law spectrum with photon index of ∼ 2, a column density of N H ∼ 5 × 10 20 cm -2 , and no prominent reflection component.Five years later, Chandra captured the source in a heavily-obscured, reflection-dominated state.The observed X-ray spectral variability could be caused by a Compton-thick cloud with N H ∼ 2 × 10 24 cm -2 eclipsing the direct emission of the hot corona, implying an extreme N H variation never before observed in a type-1 QSO.An alternative scenario is a corona that switched off in between the observations.In addition, both explanations require a significant change of the X-ray luminosity prior to the obscuration or fading of the corona and/or a change of the relative geometry of the source/reflector system.Dramatic X-ray spectral variability of this kind could be quite common in type-1 QSOs, considering the relatively few data sets in which such an event could have been identified.Our analysis implies that there may be a population of type-1 QSOs which are Compton-thick in the X-rays when observed at any given time.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".