Probing the Disk–Corona Systems and Broad-line Regions of Changing-look Quasars with X-Ray and Optical Observations

Jin, X.; Ruan, John J.; Haggard, Daryl; Gingras, M.-J.; Hountalas, J.; MacLeod, Chelsea L.; Anderson, Scott F.; Doan, Anh N.; Eracleous, Michael; Green, Paul; Runnoe, Jessie C.

doi:10.3847/1538-4357/abeb17

Cited by 6 publications

(6 citation statements)

References 91 publications

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“…There is another empirical justification for our definition of turn-off quasars. A dimming factor of 2 magnitude roughly reduces the nominal Eddington ratio of ∼ 0.1 to ∼ 0.01, where there is a change in the behavior of the X-ray-to-optical ratio α ox , indicative of a qualitative change in the accretion flow structure that signals a state transition (e.g., figure 8 in Jin et al 2021).…”

Section: Methodology and Resultsmentioning

confidence: 99%

Extreme Variability and Episodic Lifetime of Quasars

Shen

2021

Preprint

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We constrain the average episodic quasar lifetime (as in steady-state accretion) using two statistics of quasars that are recently turned off (i.e., dimmed by a large factor): 1) the fraction of turned-off quasars in a statistical sample photometrically observed over an extended period (e.g., ∆t = 20 yrs); 2) the fraction of massive galaxies that show "orphan" broad Mg ii emission, argued to be short-lived echoes of recently turned-off quasars. The two statistics constrain the average episodic quasar lifetime to be hundreds to thousands of years. Much longer (or shorter) episodic lifetimes are strongly disfavored by these observations. This average episodic lifetime is broadly consistent with the infall timescale (viscous time) in the standard accretion disk model for quasars, suggesting that quasar episodes are governed by accretion disk physics rather than by the gas supply on much larger scales. Compared with the cumulative quasar lifetime of ∼ 10 6 − 10 8 yrs constrained from quasar clustering and massive black hole demographics, our results suggest that there are ∼ 10 3 − 10 5 episodes of quasar accretion during the assembly history of the supermassive black hole. Such short episodes should be clustered over intervals of ∼ 10 4 yrs to account for the sizes of ionized narrow-line regions in quasars. Our statistical argument also dictates that there will always be a small fraction of extreme variability quasars caught in "state transitions" over multi-year observing windows, despite the much longer episodic lifetime. These transitions could occur in a rather abrupt fashion during non-steady accretion.

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Section: Methodology and Resultsmentioning

confidence: 99%

Extreme Variability and Episodic Lifetime of Quasars

Shen

2021

Preprint

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“…Strong accretion state transitions are also seen in X-ray observations of the Galactic X-ray binaries (XRBs; e.g., Maccarone 2003;Debnath et al 2010;Kara et al 2019;Wang et al 2022), suggesting analogies between AGN and XRB accretion (e.g., Ruan et al 2019;Jin et al 2021). While typical black hole (BH) accretion regions cannot yet be spatially resolved, temporal changes in XRB spectral states have gone a long way toward uncovering the accretion physics in XRBs and suggest powerful theoretical and observational analogies to AGN and quasars (Narayan 2005;Merloni et al 2003;McHardy 2010;Ruan et al 2019).…”

Section: Introductionmentioning

confidence: 95%

“…To fit the X-ray data into the full SED fit across all wavelengths, X-CIGALE uses the UV-to-X-ray slope, i.e., α OX . We use a definition of α OX following the literature (e.g., Tananbaum et al 1979;Lusso et al 2010;Ruan et al 2019;Jin et al 2021) as…”

Section: Sed Fittingmentioning

confidence: 99%

“…Figure 12 shows the behavior of α OX versus Eddington ratio, λ Edd . The gray symbols are CLQ measurements in the faint state (Ruan et al 2019;Jin et al 2021) and (ROSAT) X-ray upper limits in the bright state (lower limits in α OX , shown with upward arrows). The black symbols are three known CLQs with X-ray measurements in both states, including J0159 (Ruan et al 2019) and J2252 and J2333 (Jin et al 2021).…”

Section: Analogy Between Agn and Xrbsmentioning

confidence: 99%

“…However, for those five CLQs, only ROSAT All-Sky Survey measurements are available for the bright state, yielding upper limits on the bright-state X-ray luminosity (and thus lower limits on α OX ). Jin et al (2021) performed Chandra observations for 10 CLQs and further investigated the similarities between AGN and XRBs. However, among those 10 CLQs, only two (J2252 and J2333) had archival XMM-Newton X-ray detections in their former bright states; there are again only upper limits on the bright-state X-ray luminosity (and thus lower limits on α OX ) for the remaining eight CLQs, preventing much analysis of the changes in obscuration or X-ray spectral power-law slopes for CLQs.…”

Section: Introductionmentioning

confidence: 99%

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Probing the Origin of Changing-look Quasar Transitions with Chandra

Yang,

Green,

MacLeod

et al. 2023

ApJ

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Extremely variable quasars can also show strong changes in broad-line emission strength and are known as changing-look quasars (CLQs). To study the CLQ transition mechanism, we present a pilot sample of CLQs with X-ray observations in both the bright and faint states. From a sample of quasars with bright-state archival SDSS spectra and (Chandra or XMM-Newton) X-ray data, we identified five new CLQs via optical spectroscopic follow-up and then obtained new target-of-opportunity X-ray observations with Chandra. No strong absorption is detected in either the bright- or the faint-state X-ray spectra. The intrinsic X-ray flux generally changes along with the optical variability, and the X-ray power-law slope becomes harder in the faint state. Large-amplitude mid-infrared variability is detected in all five CLQs, and it echoes the variability in the optical with a time lag expected from the light-crossing time of the dusty torus for CLQs with robust lag measurements. The changing-obscuration model is not consistent with the observed X-ray spectra and spectral energy distribution changes seen in these CLQs. It is highly likely that the observed changes are due to the changing accretion rate of the supermassive black hole, so the multiwavelength emission varies accordingly, with promising analogies to the accretion states of X-ray binaries.

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An accretion disc with magnetic outflows triggered by a sudden mass accretion event in changing-look active galactic nucleus 1ES 1927+654

Cao,

You,

Wei

2023

Monthly Notices of the Royal Astronomical Society

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1ES 1927+654 was known as a type 2 Seyfert galaxy, which exhibited drastic variability recently in ultraviolet (UV)/optical and X-ray bands. An UV/optical outburst was observed in the end of 2017, and it reached the peak luminosity ∼50 days later. The high-cadence observations showed a rapid X-ray flux decline with complete disappearance of the power-law hard X-ray component when the soft X-ray thermal emission reached its lowest level about 150 days after the UV/optical peak. The power law X-ray component reappeared with thermal X-ray emission brightening from its lowest flux within next ∼ 100 days. We assume an episodic accretion event taking place in the outer region of the disc surrounding a central black hole (BH), which is probably due to a red giant star tidally disrupted by the BH. The inner thin disc with corona is completely swept by the accretion event when the gas reaches the innermost circular stable orbit. The field threading the disrupted star is dragged inwards by the disc formed after the tidal disruption event, which accelerates outflows from the disc. The disc dimmed since a large fraction of the energy released in the disc is tapped into the outflows. The accretion rate of the episodic accretion event declines, and ultimately it turns out to be a thin disc, which is inefficient for field advection, and the outflows are switched off. A thin disc with corona reappears later after the outburst.

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Probing the Disk–Corona Systems and Broad-line Regions of Changing-look Quasars with X-Ray and Optical Observations

Cited by 6 publications

References 91 publications

Extreme Variability and Episodic Lifetime of Quasars

Extreme Variability and Episodic Lifetime of Quasars

Probing the Origin of Changing-look Quasar Transitions with Chandra

An accretion disc with magnetic outflows triggered by a sudden mass accretion event in changing-look active galactic nucleus 1ES 1927+654

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