Changing looks of the nucleus of the Seyfert galaxy <scp>NGC</scp> 1566 compared with other changing‐look <scp>AGNs</scp>

Oknyansky, Victor

doi:10.1002/asna.20210080

Cited by 5 publications

(3 citation statements)

References 43 publications

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“…The recent multiwavelength campaign, including the Swift data [38], revealed that the dramatic change in broad line profiles was actually proceeded with the strong outburst in X-rays in 2020, which showed the increase in a few orders of magnitude. A comparable increase in the X-ray flux has been observed in other CL AGNs, such as NGC 1566 [74] or HE 1136-2304 [75]. As a conclusion, Ref.…”

Section: Discussionsupporting

confidence: 81%

Long-Term Optical Monitoring of Broad-Line AGNs (LoTerm AGN): Case Study of NGC 3516

Ilić,

Popović,

Burenkov

et al. 2023

Physics

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Properties of the broad line region (BLR) in active galactic nuclei (AGNs) are commonly used to estimate the mass of the supermassive black hole (SMBH) that powers an AGN. However, the understanding of the physics behind the BLR remains incomplete. The AGNs exhibit strong optical variability, observed in the change of the profiles and fluxes of broad emission lines. Utilizing this variability provides an opportunity to constrain the physics of the BLR, and understand the interplay of the BLR with SMBH and surrounding regions. Here, we present the long-term monitoring campaign of a sample of the known broad-line AGNs (identified as LoTerm AGN). The aim of this study is to show the importance of sustained and dedicated campaigns that continually collect spectroscopic data of the known AGNs over extended timescales, providing unique insight into the origin and structure of the BLR. LoTerm AGN is a collaborative network of seven moderate-size telescopes equipped for spectroscopy. We focus on the recent spectral data of the known changing-look AGN, NGC 3516. Specifically, we examine the broad hydrogen Balmer Hα line observed in the period 2020–2023, demonstrating that this AGN remains active with the BLR signatures observed in the spectra. No significant change in the broad line profile of Hα line is observed during this recent period.

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Section: Discussionsupporting

confidence: 81%

Long-Term Optical Monitoring of Broad-Line AGNs (LoTerm AGN): Case Study of NGC 3516

Ilić,

Popović,

Burenkov

et al. 2023

Physics

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“…The BASS catalogue contains some of the most well-known and well-studied AGN in the local universe, including many that had previously been observed to change type. Fairall 9 (BAT 73), NGC 1566 (BAT 216), HE 1136-2304 (BAT 557), KUG 1141+371 (BAT 565), NGC 4151 (BAT 595), 3C 390.3 (BAT 994), NGC 7582 (BAT 1188), NGC 7603 (BAT 1189) and IRAS 23226-3843 (BAT 1194) have all been observed to show CL behaviour (Tohline & Osterbrock 1976;Penston & Perez 1984;Kollatschny & Fricke 1985;Wamsteker et al 1985;Malkov et al 1997;Aretxaga et al 1999;Kollatschny et al 2000;Shapovalova et al 2008;Parker et al 2016;Oknyansky et al 2019;Kollatschny et al 2020;Jiang et al 2021;Liu et al 2022;Oknyansky 2022). These nine AGN are shown with green circles in Fig.…”

Section: Previously Known CL Eventsmentioning

confidence: 97%

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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“…The local Seyfert NGC 1566 is one of the first CLAGN ever discovered (Pastoriza & Gerola 1970). Its variability has been widely studied from the optical, to the UV and X-ray energies, revealing a dramatic variability of emission line profiles and recurrent brightening events (Alloin et al 1986;da Silva et al 2017;Oknyansky et al 2019;Oknyansky 2022). The changing state of NGC 1566 was interpreted as the result of a luminosity increase causing the sublimation of dust in the line of sight, which previously obscured part of the BLR.…”

Section: Introductionmentioning

confidence: 99%

The optically elusive, changing-look active nucleus in NGC 4156

Tozzi

Lusso

Casetti

et al. 2022

A&A

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We report on the changing-look nature of the active galactic nucleus (AGN) in the galaxy NGC 4156, as serendipitously discovered thanks to data acquired in 2019 at the Telescopio Nazionale Galileo (TNG) during a students' observing programme. Previous optical spectra had never shown any signatures of broad-line emission, and evidence of the AGN had come only from X-ray observations, being the optical narrow-line flux ratios unable to unambiguously denote this galaxy as a Seyfert. Our 2019 TNG data unexpectedly revealed the appearance of broad-line components in both the Hα and Hβ profiles, along with a rise of the continuum, thus implying a changing-look AGN transitioning from a type 2 (no broad-line emission) towards a (nearly) type 1. The broad-line emission has then been confirmed by our 2022 follow-up observations, whereas the rising continuum has no longer been detected, which hints at a further evolution backwards to a (nearly) type 2. The presence of broad-line components also allowed us to obtain the first singleepoch estimate of the black hole mass (log(M BH /M ) ∼ 8.1) in this source. The observed spectral variability might be the result of a change in the accretion activity of NGC 4156, although variable absorption cannot be completely excluded.

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Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing‐look AGNs

Cited by 5 publications

References 43 publications

Long-Term Optical Monitoring of Broad-Line AGNs (LoTerm AGN): Case Study of NGC 3516

Long-Term Optical Monitoring of Broad-Line AGNs (LoTerm AGN): Case Study of NGC 3516

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

The optically elusive, changing-look active nucleus in NGC 4156

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