Comparative Photometry of the Quiet Quasar PDS 456 and the Radio-Loud Blazar 3C 273
Bibliographic record
Abstract
A comparative analysis of the photometric variability of the blazar 3C 273 and the quasar PDS 456 using multi-band data from ground- and space-based platforms (2015–2025) reveals contrasting behaviors. For 3C 273, a statistically significant secular dimming was detected in the ATLASc-band light curve (5.6±0.2)×10−4magday−1 and confirmed by Johnson–Cousins V-band photometry. Ten optical flares were identified, two coinciding with Fermi gamma-ray enhancements, suggesting a synchrotron origin linked to jet activity. A significant bluer-when-brighter trend (ρ=−0.54) was found relative to the o-band, and several color extrema align with gamma-ray activity, reinforcing the nonthermal interpretation. In contrast, PDS 456 exhibits a statistically significant secular brightening in the o-band (−3.1±0.2)×10−5magday−1 and 75 optical flares, four coinciding with UV flares observed by Swift/UVOT. The c–o color index displays a non-Gaussian distribution with asymmetric reddening and blueing episodes. An extreme reddening event aligns with a strong UV flare, suggesting transient inner-disk heating. These results indicate jet-dominated variability in 3C 273 and disk-driven variability in PDS 456, highlighting distinct physical mechanisms in radio-loud versus radio-quiet active galactic nuclei.
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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 | 0.001 | 0.001 |
| 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".