A Transient “Changing-look” Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data

Zeltyn, Grisha; Trakhtenbrot, Benny; Eracleous, Michael; Runnoe, Jessie C.; Trump, Jonathan R.; Stern, Jonathan; Shen, Yue; Hernández-García, L.; Bauer, F. E.; Yang, Qian; Dwelly, T.; Ricci, Cláudio; Green, Paul; Anderson, Scott F.; Assef, Roberto J.; Guolo, Muryel; MacLeod, Chelsea L.; Davis, Megan C.; Fries, Logan B.; Gezari, Suvi; Grogin, Norman A.; Homan, David; Koekemoer, Anton M.; Krumpe, M.; LaMassa, Stephanie; Liu, Xin; Merloni, A.; Martínez-Aldama, Mary Loli; Schneider, Donald P.; Temple, Matthew J.; Brownstein, Joel R.; Ibarra-Medel, H.; Burke, J.; Pellegrino, C.; Kollmeier, Juna A.

doi:10.3847/2041-8213/ac9a47

Cited by 16 publications

(22 citation statements)

References 57 publications

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“…Over 100 CL AGNs have been discovered based on their Balmer-line profile transitions (MacLeod et al 2016;Gezari et al 2017;Sheng et al 2017;Frederick et al 2019;Green et al 2022;Hon et al 2022;Zeltyn et al 2022;Chen et al 2023;Yang et al 2023), and dozens of CL AGNs have also been identified based on transitions in Mg II, C III], and C IV (Guo et al 2019(Guo et al , 2020Ross et al 2020). However, the nature and frequency of CL AGNs are still not well understood, and many questions remain unanswered.…”

Section: Introductionmentioning

confidence: 99%

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data

Guo,

Zou,

Fawcett

et al. 2024

ApJS

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Changing-look active galactic nuclei (CL AGNs) can be generally confirmed by the emergence (turn-on) or disappearance (turn-off) of broad emission lines (BELs), associated with a transient timescale (about 100 ∼ 5000 days) that is much shorter than predicted by traditional accretion disk models. We carry out a systematic CL AGN search by crossmatching the spectra coming from the Dark Energy Spectroscopic Instrument and the Sloan Digital Sky Survey. Following previous studies, we identify CL AGNs based on Hα, Hβ, and Mg ii at z ≤ 0.75 and Mg ii, C iii], and C iv at z > 0.75. We present 56 CL AGNs based on visual inspection and three selection criteria, including 2 Hα, 34 Hβ, 9 Mg ii, 18 C iii], and 1 C iv CL AGN. Eight cases show simultaneous appearances/disappearances of two BELs. We also present 44 CL AGN candidates with significant flux variation of BELs, but remaining strong broad components. In the confirmed CL AGNs, 10 cases show additional CL candidate features for different lines. In this paper, we find: (1) a 24:32 ratio of turn-on to turn-off CL AGNs; (2) an upper-limit transition timescale ranging from 330 to 5762 days in the rest frame; and (3) the majority of CL AGNs follow the bluer-when-brighter trend. Our results greatly increase the current CL census (∼30%) and would be conducive to exploring the underlying physical mechanism.

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Section: Introductionmentioning

confidence: 99%

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data

Guo,

Zou,

Fawcett

et al. 2024

ApJS

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“…However, we know that at least some CL transitions occur on much shorter timescales (e.g. Gezari et al 2017;Trakhtenbrot et al 2019;Zeltyn et al 2022) which we would miss in cases where a source transitions twice (e.g. off and then on again) within ≈300 days.…”

Section: Time-scales Of CL Eventsmentioning

confidence: 96%

BASS XXXIX: Swift-BAT AGN with changing-look optical spectra

Temple,

Ricci,

Koss

et al. 2022

Preprint

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Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time, where the appearance or disappearance of broad Balmer line emission leads to a change in the observed Seyfert type classification. Combining with known events from the literature, 21 AGN from BASS are now known to display CL behaviour. Nine CL events have 14-195 keV data available, and five of these CL events can be associated with significant changes in their 14-195 keV flux from BAT. The ultra-hard X-ray flux is less affected by obscuration and so these changes in the 14-195 keV band suggest that the majority of our CL events are not due to changes in line-of-sight obscuration. We derive a CL rate of 0.7-6.2 per cent on 10-25 year time-scales, and show that many transitions happen within at most a few years. Our results motivate further multi-wavelength observations with higher cadence to better understand the variability physics of accretion onto SMBHs.

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“…While constant reddening should not affect the variability amplitudes, it does affect the relative luminosities between wavelength bands, and consequently our model fit results. In addition, a hypervariable quasar with dramatically variable reddening has recently been discovered from SDSS-V (Zeltyn et al 2022). Variable reddening would alter the variability amplitude and the likely reprocessing geometry of the hypervariable quasar.…”

Section: Host-galaxy Contributions and Reddeningmentioning

confidence: 99%

Reprocessing Models for the Optical Light Curves of Hypervariable Quasars from the Sloan Digital Sky Survey Reverberation Mapping Project

Akiba,

Dexter,

Brandt

et al. 2023

ApJ

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We explore reprocessing models for a sample of 17 hypervariable quasars, taken from the Sloan Digital Sky Survey Reverberation Mapping project, which all show coordinated optical luminosity hypervariability with amplitudes of factors ≳2 between 2014 and 2020. We develop and apply reprocessing models for quasar light curves in simple geometries that are likely to be representative of quasar inner environments. In addition to the commonly investigated thin-disk model, we include the thick-disk and hemisphere geometries. The thick-disk geometry could, for instance, represent a magnetically elevated disk, whereas the hemisphere model can be interpreted as a first-order approximation for any optically thick out-of-plane material caused by outflows/winds, warped/tilted disks, and so on. Of the 17 quasars in our sample, 11 are best-fitted by a hemisphere geometry, five are classified as thick disks, and both models fail for just one object. We highlight the successes and shortcomings of our thermal reprocessing models in case studies of four quasars that are representative of the sample. While reprocessing is unlikely to explain all of the variability that we observe in quasars, we present our classification scheme as a starting point for revealing the likely geometries of reprocessing for quasars in our sample and hypervariable quasars in general.

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A Transient “Changing-look” Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data

Cited by 16 publications

References 57 publications

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data

Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. I. Sample from the Early Data

BASS XXXIX: Swift-BAT AGN with changing-look optical spectra

Reprocessing Models for the Optical Light Curves of Hypervariable Quasars from the Sloan Digital Sky Survey Reverberation Mapping Project

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