Changing-Look Narrow-Line Seyfert 1 Galaxies, their Detection with SVOM, and the Case of NGC 1566

Xu, D. W.; Komossa, S.; Grupe, D.; Wang, J.; Xin, L. P.; Han, X. H.; Wei, J. Y.; Bai, J. Y.; Bon, E.; Cangemi, F.; Cordier, B.; Dennefeld, M.; Gallo, L. C.; Kollatschny, W.; Kong, De-Feng; Ochmann, M. W.; Qiu, Y. L.; Schartel, N.

doi:10.3390/universe10020061

Cited by 4 publications

(2 citation statements)

References 102 publications

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“…The X-ray outbursts seen in 1990 by ROSAT and 2010 by Swift are most likely caused by an accretion-disk instability as favored by Grupe et al (2015), since IC 3599 is not a quiescent galaxy but a bona fide AGN. In fact, IC 3599 is an extreme case of an optical changing-look AGN (Komossa & Grupe 2023;Xu et al 2024).…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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 argue that the Bondi accretion scenario is helpful for explaining the rare detection of the CL phenomenon of narrowline Seyfert 1 galaxies (NLS1s). To date, there are only five CL-NLS1s (e.g., Oknyansky et al 2018;Frederick et al 2019;MacLeod et al 2019;Hon et al 2022;Xu et al 2024). Taking into account their small SMBHs (M BH ∼ 10 7 M e ) and high accretion rate close to the Eddington limit (e.g., Boroson 2002;Grupe 2004;Xu et al 2012; see Komossa 2008 for a review), the rarity of CL-NLS1s could be explained in terms of the proposed Bondi accretion scenario because of the very long CL cycle time (∼10 3 yr) predicted by Equation (3).…”

Section: Mass Transfer Instabilitymentioning

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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The transient event in NGC 1566 from 2017 to 2019

Ochmann,

Kollatschny,

Probst

et al. 2024

A&A

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is a local face-on Seyfert galaxy and is known for exhibiting recurrent outbursts that are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported to be accompanied by a change in Seyfert classification from Seyfert 1.8 to Seyfert 1.2. We aim to study the transient event in detail by analyzing the variations in the optical broad-line profiles. In particular, we intend to determine the structure and kinematics of the broad-line region. We analyzed data from an optical spectroscopic variability campaign of taken with the 9.2\,m Southern African Large Telescope (SALT) between July 2018 and October 2019 triggered by the detection of hard X-ray emission in June 2018. We supplemented this data set with optical to near-infrared (NIR) spectroscopic archival data taken by VLT/MUSE in September 2015 and October 2017, and investigated the emission from different line species during the event. exhibits pronounced spectral changes during the transient event. We observe the emergence and fading of a strong power-law-like blue continuum as well as strong variations in the Balmer He i and He ii lines and the coronal lines Fe vii Fe X and Fe XI . Moreover, we detect broad double-peaked emission line profiles of O i and the Ca ii triplet. This is the first time that genuine double-peaked O i and Ca ii emission in AGN is reported in the literature. All broad lines show a clear redward asymmetry with respect to their central wavelength and we find indications for a significant blueward drift of the total line profiles during the transient event. The profiles and the FWHM of the Balmer lines remain largely constant during all observations. We show that the double-peaked emission line profiles are well approximated by emission from a low-inclination, relativistic eccentric accretion disk, and that single-peaked profiles can be obtained by broadening due to scale-height-dependent turbulence. Small-scale features in the O i and Ca ii lines suggest the presence of inhomogeneities in the broad-line region. We conclude that the broad-line region in is dominated by the kinematics of a relativistic eccentric accretion disk. The broad-line region can be modeled to be vertically stratified with respect to scale-height turbulence with O i and Ca ii being emitted close to the disk in a region with high (column) density, while the Balmer and helium lines are emitted at greater scale height above the disk. The observed blueward drift might be attributed to a low-optical-depth wind launched during the transient event. Except for this wind, the observed kinematics of the broad-line region remain largely unchanged during the transient event.

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Changing-Look Narrow-Line Seyfert 1 Galaxies, their Detection with SVOM, and the Case of NGC 1566

Cited by 4 publications

References 102 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

The transient event in NGC 1566 from 2017 to 2019

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