Multiwavelength study of extreme variability in LEDA 1154204: A changing-look event in a type 1.9 Seyfert
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Bibliographic record
Abstract
Context. Multiwavelength studies of transients in actively accreting supermassive black holes have revealed that large-amplitude variability is frequently linked to significant changes in the optical spectra. This phenomenon is known as a changing-look active galactic nucleus (CLAGN). Aims. In 2020, the Zwicky Transient Facility detected a transient flaring event in the type 1.9 AGN LEDA 1154204, wherein the brightness sharply increased by 0.55 mag in one month and then began to decay. Spectrum Roentgen Gamma (SRG)/eROSITA also observed the object as part of its all-sky X-ray surveys after the flare had started to decay. Methods. We performed a three-year multiwavelength follow-up campaign to track the spectral and temporal characteristics of the source during the post-flare fading. This campaign included optical spectroscopy, X-ray spectroscopy and photometry, and ultraviolet, optical, and infrared continuum photometry. Results. Optical spectra taken near the flare peak revealed a broad double-peaked H β emission and a blue continuum, neither of which were detected in a 2005 archival spectrum. The broad H β had increased by a factor of > 5–6. From late 2020 through 2023, the broad Balmer-line flux faded as the continuum faded, and the Balmer decrement increased by ∼2.2. This is consistent with the expected ionization response. The X-ray spectrum exhibits no significant spectral variability despite dramatic flux variation of a factor of 17. There is no evidence of a soft X-ray excess, which indicates an energetically unimportant warm corona. Conclusions. The transient event was likely triggered by a disk instability in a preexisting AGN-like accretion flow that culminated in the observed multiwavelength variability (X-rays via thermal Comptonization, illumination of the broad-line region, and infrared dust echo) and in the CLAGN event.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it