Autor: |
Shu Wang, Jong-Hak Woo, Elena Gallo, Hengxiao Guo, Donghoon Son, Minzhi Kong, Amit Kumar Mandal, Hojin Cho, Changseok Kim, Jaejin Shin |
Jazyk: |
angličtina |
Rok vydání: |
2024 |
Předmět: |
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Zdroj: |
The Astrophysical Journal, Vol 966, Iss 1, p 128 (2024) |
Druh dokumentu: |
article |
ISSN: |
1538-4357 |
DOI: |
10.3847/1538-4357/ad3049 |
Popis: |
Changing-look (CL) active galactic nuclei (AGNs), characterized by the appearance/disappearance of broad emission lines in the span of a few years, present a challenge for the AGN unified model, whereby the Type 1 versus Type 2 dichotomy results from orientation effects alone. We present a systematic study of a large sample of spectroscopically classified AGNs, using optical variability data from the Zwicky Transient Facility (ZTF) as well as follow-up spectroscopy data. We demonstrate that Type 1 and Type 2 AGNs can be neatly separated on the basis of the variability metric σ _QSO , which quantifies the resemblance of a light curve to a damped random walk model. For a small subsample, however, the ZTF light curves are inconsistent with their previous classification, suggesting the occurrence of a CL event. Specifically, we identify 35 (12) turn-on (turn-off) CL AGN candidates at z < 0.35. Based on follow-up spectroscopy, we confirm 17 (4) turn-on (turn-off) CL AGNs out of 21 (5) candidates, representing a high success rate for our method. Our results suggest that the occurrence rate of CL AGNs is ∼0.3% over timescales of 5–20 yr, and confirm that the CL transition typically occurs at an Eddington ratio of ≲0.01. |
Databáze: |
Directory of Open Access Journals |
Externí odkaz: |
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