Identifying Changing-look AGNs Using Variability Characteristics

Wang, Shu; Woo, Jong-Hak; Gallo, Elena; Guo, Hengxiao; Son, Donghoon; Kong, Minzhi; Mandal, Amit Kumar; Cho, Hojin; Kim, Changseok; Shin, Jaejin

doi:10.3847/1538-4357/ad3049

Cited by 4 publications

(2 citation statements)

References 101 publications

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“…The V filter data are dominated by white noise. This variability pattern is typical for type 2 AGN (Wang et al 2024) and may suggest that IC 3599 remains in its Seyfert 1.9 state at this time.…”

Section: Variability Analysismentioning

confidence: 63%

The Calm Before the (Next) Storm: No Third Outburst in 2019–2020, and Ongoing Monitoring of the Transient AGN IC 3599

Grupe,

Komossa,

Wolsing

2024

ApJ

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We report on follow-up observations of the Seyfert 1.9 galaxy IC 3599 with the NASA Neil Gehrels Swift mission. The detection of a second X-ray outburst in 2010 by Swift after the first discovery of a bright X-ray outburst in 1990 by ROSAT led to the suggestion of two very different explanations. The first one assumed that IC 3599 exhibits outbursts due to repeated partial tidal stripping of a star, predicting another outburst of IC 3599 in 2019/2020. The second, alternative scenario assumed that the event observed in X-rays is due to an accretion-disk instability, which would suggest a much longer period between the large outbursts. Our continued monitoring campaign by Swift allowed us to test the first scenario that predicted a repetition of high-amplitude flaring activity in 2019/2020. We do not find any evidence of dramatic flaring activity with factors of 100 since the last X-ray outburst seen in 2010. These observations support the accretion-disk scenario. Further, while IC 3599 remains in low-emission states, the long-term X-ray light curve of IC 3599 reveals ongoing strong variability of a factor of a few. The most remarkable event is a miniflare of a factor of 10 in X-rays in 2022 December. After that flare, the otherwise supersoft X-ray spectrum shows an exceptional hardening, reminiscent of a temporary corona formation.

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Section: Variability Analysismentioning

confidence: 63%

The Calm Before the (Next) Storm: No Third Outburst in 2019–2020, and Ongoing Monitoring of the Transient AGN IC 3599

Grupe,

Komossa,

Wolsing

2024

ApJ

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“…The identification of CL-AGNs has surged dramatically due to recent advancement in multiepoch spectroscopy. However, the number of confirmed CL-AGNs remains limited, with ∼400 instances identified (e.g., López-Navas et al 2022Guo et al 2024;Wang et al 2023Wang et al 2024aZeltyn et al 2024). Out of these, only 11 repeating CL-AGNs (RCL-AGNs) have exhibited repeated type transitions (Marin et al 2019;Wang et al 2020, 2022 andreferences therein).…”

Section: Introductionmentioning

confidence: 99%

Instability of Circumnuclear Gas Supply as an Origin of the “Changing-look” Phenomenon of Supermassive Black Holes

Wang,

Xu,

Cao

et al. 2024

ApJ

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The origin of the “changing-look” (CL) phenomenon in supermassive black holes (SMBHs) remains an open issue. This study aims to shed light on this phenomenon by focusing on a sample that encompasses all known repeating CL active galactic nuclei (AGNs). Through the identification of a characteristic timescale for the CL phenomenon, it was observed that larger SMBHs possess shorter characteristic timescales, while smaller SMBHs exhibit longer timescales. These findings reveal a significant contrast to the traditional AGN variability that has been adequately explained by the AGN’s disk instability model. This stark discrepancy highlights a distinct origin of the CL phenomenon, distinguishing it from traditional AGN variability. By properly predicting the characteristic timescale and its dependence on SMBH mass, we propose that the CL phenomenon is likely a result of a variation in accretion rate caused by a sudden change in the supply of circumnuclear gas during the transition between active and passive SMBH fueling stages.

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How Long Will the Quasar UV/Optical Flickering Be Damped? II. The Observational Test

Ren,

Zhou,

Sun

et al. 2024

ApJ

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The characteristic timescale at which the variability of active galactic nuclei (AGNs) turns from red noise to white noise can probe the accretion physics around supermassive black holes (SMBHs). A number of works have studied the characteristic timescale of quasars and obtained quite different scaling relations between the timescale and quasar physical properties. One possible reason for the discrepancies is that the characteristic timescale can be easily underestimated if the light curves are not long enough. In this work, we construct well-defined AGN samples to observationally test the relationships between the characteristic timescale and AGN properties obtained by previous works. Our samples eliminate the effects of insufficient light-curve lengths. We confirm that the timescale predictions of the Corona Heated Accretion disk Reprocessing model are consistent with our timescale measurements. The timescale predictions by empirical relations are systematically smaller than our measured ones. Our results provide further evidence that AGN variability is driven by thermal fluctuations in SMBH accretion disks. Future flagship time-domain surveys can critically test our conclusions and reveal the physical nature of AGN variability.

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Identifying Changing-look AGNs Using Variability Characteristics

Cited by 4 publications

References 101 publications

The Calm Before the (Next) Storm: No Third Outburst in 2019–2020, and Ongoing Monitoring of the Transient AGN IC 3599

The Calm Before the (Next) Storm: No Third Outburst in 2019–2020, and Ongoing Monitoring of the Transient AGN IC 3599

Instability of Circumnuclear Gas Supply as an Origin of the “Changing-look” Phenomenon of Supermassive Black Holes

How Long Will the Quasar UV/Optical Flickering Be Damped? II. The Observational Test

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