Changing-look active galactic nuclei: close binaries of supermassive black holes in action

Wang, Jian-Min; Bon, E.

doi:10.1051/0004-6361/202039368

Cited by 36 publications

(27 citation statements)

References 79 publications

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“…Moreover, it could be that the CL phenomenon is a common phase, and that it could be detected in each strongly variable AGN if constantly observed (see discussion in Oknyansky et al 2017). The CL transition could be caused by the intrinsic changes of accretion disk, obscuration of the BLR, tidal disruption events, or even presence of the close binary SMBH (Wang & Bon 2020). Therefore, understating these object could help shedding light on understanding the AGN structure and evolution.…”

Section: Oscillatory Patterns In Agn Light Curvesmentioning

confidence: 98%

“…Physical processes causing such dramatic change are still unknown (e.g. , but this could be also a signature of a presence of close binary SMBH (Wang & Bon 2020). So far, surveys have discovered only a small fraction of changing-look candidates (e.g., Runco et al 2016, MacLeod et al 2016), but future surveys like the LSST will be able to discover many or even show that this phase is not so rare.…”

Section: Time-domain Astronomy Of Agnsmentioning

confidence: 99%

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Investigation of active galactic nuclei in time domain era

Ilic,

Kovacevic,

Popovic

2021

Preprint

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The perfect case for time-domain investigations are active galactic nuclei (AGNs) since they are luminous objects that show strong variability. Key result from the studies of AGNs variability is the estimated mass of a supermassive black hole (SMBH), which resides in the center of an AGN. Moreover, the spectral variability of AGN can be used to study the structure and physics of the broad line region, which in general can be hardly directly observed. Here we review the current status of AGNs variability investigations in Serbia, in the perspectives of the present and future monitoring campaigns.spectroscopy, with its unique capability to study up to 4,000 astronomical objects at once. It will provide spectral light curves of the largest number of quasars, which analysis will enable mapping of the inner regions in AGNs (Shen et al. 2019).This motivates us to do investigations of AGNs using optical spectroscopy in timedomain, of which recent results we give an overview in this Proceedings. We cover topics from: i) long-term monitoring campaign of the sample of near-by AGNs, ii) studies of oscillations in AGN light curves in search for periodic signals, iii) studies of the optically extremely variable AGNs. The findings of our research project are put in the concept of applications and impact to future large surveys, especially the LSST. These investigations are done at the Astronomical Observatory in Belgrade and the Department of Astronomy of the Faculty of Mathematics, University of Belgrade, mainly through the project of "Astrophysical spectroscopy of extragalactic objects", 176001, supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, which was financed by the end of 2019. This paper is organized as follows: in Sec. 2 we shortly describe the theoretical background of AGN structure, and give the current overview of time-domain investigation of AGNs, in Sec. 3 we list some of the major results of our findings, in Sec. 4 put them in concept of future surveys, and in Sec. 5 a short summary is given. OVERVIEW OF AGNs AND TIME-DOMAIN INVESTIGATIONS 1. ACTIVE GALACTIC NUCLEI

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Section: Oscillatory Patterns In Agn Light Curvesmentioning

confidence: 98%

Section: Time-domain Astronomy Of Agnsmentioning

confidence: 99%

Investigation of active galactic nuclei in time domain era

Ilic,

Kovacevic,

Popovic

2021

Preprint

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“…We have investigated the detection of individual SMBBHs by current and future PTAs and its possible cosmological application to constrain cosmological parameters [634][635][636]. We have found a number of SMBBH candidates [637,638], investigated the detailed observational properties of some SMBBH candidates [639,640], and introduced several new methods to identify BBH candidates and distinguish it from alternative interpretations [641][642][643][644], investigated the cosmic evolution of SMBBHs and predicted the SGWBs resulting from inspiralling SMBBHs and SMBBH merger rate [645].…”

Section: Gw Astrophysicsmentioning

confidence: 99%

The Gravitational-wave physics II: Progress

Bian

Cai

Cao

et al. 2021

Sci. China Phys. Mech. Astron.

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It has been a half-decade since the first direct detection of gravitational waves, which signifies the coming of the era of the gravitational-wave astronomy and gravitational-wave cosmology. The increasing number of the detected gravitational-wave events has revealed the promising capability of constraining various aspects of cosmology, astronomy, and gravity. Due to the limited space in this review article, we will briefly summarize the recent progress over the past five years, but with a special focus on some of our own work for the Key Project "Physics associated with the gravitational waves" supported by the National Natural Science Foundation of China. In particular, (1) we have presented the mechanism of the gravitational-wave production during some physical processes of the early Universe, such as inflation, preheating and phase transition, and the cosmological implications of gravitational-wave measurements; (2) we have put constraints on the neutron star maximum mass according to GW170817 observations; (3) we have developed a numerical relativity algorithm based on the finite element method and a waveform model for the binary black hole coalescence along an eccentric orbit.

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“…Also, some other types of AGN such as Changing-look AGN (CL-AGNs) as a new subpopulation (see e.g. notable case of NGC 3516, Shapovalova et al 2019, Ilić et al 2020, Feng et al 2021) challenge some fundamental physics of AGNs so that a possible explanantion for them is that CB-SMBHs with high eccentricities are able to trigger the CL transition through one orbit (see Wang and Bon 2020). This review focuses on RM and spectroastrometry observational signatures of CB-SMBHs with non-zero eccentricity from numerical simulations with particular attention to recent developments and open issues.…”

Section: Introductionmentioning

confidence: 99%

Investigating close binary supermassive black holes at high angular resolution

Kovačević

2021

SERBIAN ASTRON J

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Gravitational waves (GW) in the nano-Hz domain are expected to be radiated by close-binaries of supermassive black holes (CB-SMBHs; components bound in a Keplerian binary at mutual distance less than ~ 0.1 pc), which are relicts of galaxy mergers and anticipated to be measured via the Pulsar Timing Array (PTA) technique. The challenge of present CB-SMBH investigations is that their signatures are elusive and not easily disentangled from a single SMBH. PTAs will typically have a glimpse of an early portion of the binary inspiral to catch the frequency evolution of the binary only with sufficiently high mass and initially high eccentricity. Thus, we have to make use of electromagnetic observations to determine orbital parameters of CB-SMBHs and test nano-Hz GW properties. The 2D reverberation mapping (RM) is a powerful tool for probing kinematics and geometry of ionized gas in the SMBHs (single or binary) vicinity, yet it can lose information due to projection on the line of sight of the observer. Nevertheless, spectroastrometry with AMBER, GRAVITY, and successors can provide an independent measurement of the emitting region's size, geometry, and kinematics. These two techniques combined can resolve CB-SMBHs. In this review, we focus on RM and spectroastrometry observational signatures of CB-SMBHs with non-zero eccentricity from recent simulations with particular attention to recent developments and open issues.

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Changing-look active galactic nuclei: close binaries of supermassive black holes in action

Cited by 36 publications

References 79 publications

Investigation of active galactic nuclei in time domain era

Investigation of active galactic nuclei in time domain era

The Gravitational-wave physics II: Progress

Investigating close binary supermassive black holes at high angular resolution

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