New changing look case in NGC 1566

Oknyansky, V. L.; Winkler, Hartmut; Tsygankov, Sergey S.; Липунов, В. М.; Gorbovskoy, E.; Wyk, F. van; Buckley, D.; Tyurina, N.

doi:10.1093/mnras/sty3133

Cited by 80 publications

(100 citation statements)

References 42 publications

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“…The blended profile of [O I] λ6363 and [Fe x] λ6374 was also fitted (see Fig.5, upper panel). From the fit, the estimated ratio of [O I]+[Fe x] to [O I] λ6300 is ∼1.2, similar that observed in NGC 1566 during the brightening phase (Oknyansky et al 2019b), but we note that it is strongly dependent on the estimated level of the underlying continuum and Hα extended wing. From the clear single profile of [Fe vii] λ6087 (see Fig.3), we estimated that the line fluxes have increased by the factor of approximately two compared to the last published data of Shapovalova et al (2019).…”

Section: Analysis and Resultssupporting

confidence: 82%

A flare in the optical spotted in the changing-look Seyfert NGC 3516

Ilić

Tsygankov

Belinski

et al. 2020

A&A

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Context. We present observations from the short-term intensive optical campaign (from September 2019 to January 2020) of the changing-look Seyfert NGC 3516. This active galactic nucleus is known to have strong optical variability and has changed its type in the past. It has been in the low-activity state in the optical since 2013, with some rebrightening from the end of 2015 to the beginning of 2016, after which it remained dormant. Aims. We aim to study the photometric and spectral variability of NGC 3516 from the new observations in U-and B-bands and examine the profiles of the optical broad emission lines in order to demonstrate that this object may be entering a new state of activity. Methods. NGC 3516 has been monitored intensively for the past 4 months with an automated telescope in U and B filters, enabling accurate photometry of 0.01 precision. Spectral observations were triggered when an increase in brightness was spotted. We support our analysis of past-episodes of violent variability with the UV and X-ray long-term light curves constructed from the archival Swift/UVOT and Swift/XRT data.Results. An increase of the photometric magnitude is seen in both U and B filters to a maximum amplitude of 0.25 mag and 0.11 mag, respectively. During the flare, we observe stronger forbidden high-ionization iron lines ([Fe vii] and [Fe x]) than reported before, as well as the complex broad Hα and Hβ lines. This is especially seen in Hα, which appears to be double-peaked. It seems that a very broad component of ∼10,000 km s −1 in width in the Balmer lines is appearing. The trends in the optical, UV, and X-ray light curves are similar, with the amplitudes of variability being significantly larger in the case of UV and X-ray bands. Conclusions. The increase of the continuum emission, the variability of the coronal lines, and the very broad component in the Balmer lines may indicate that the AGN of NGC 3516 is finally leaving the low-activity state in which it has been for the last ∼3 years.

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Section: Analysis and Resultssupporting

confidence: 82%

A flare in the optical spotted in the changing-look Seyfert NGC 3516

Ilić

Tsygankov

Belinski

et al. 2020

A&A

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“…As noted in many studies of local AGNs displaying temporal spectral variabilities (e.g. NGC548 and NGC4151) (Landt et al 2015;Rose et al 2015;Oknyansky et al 2019 Regardless what physical processes are producing the flare, several properties of the broad and narrow line emitting regions can be inferred from time lags between continuum and spectral lines, and line ratio diagnostics.…”

Section: Temporal Behavior -Constant Broad Hα Line and Variable Narromentioning

confidence: 95%

“…Gezari et al 2017), or 1 http://www.astronomy.ohio-state.edu/∼assassin/index.shtml spectral change between a type 2 and a type 1 AGN (e.g Ruan et al 2016;Runnoe et al 2016), or periodic photometric variations (several years time scale) in some AGNs (Oknyanskij 1978;Oknyanskij & Lyuty 2007;Graham et al 2015;Jun et al 2015;Bon et al 2016). Both TDEs and CLAGNs have become the focus of many recent studies (Gezari et al 2012;Yang et al 2013;MacLeod et al 2016;Ruan et al 2016;Runnoe et al 2016;Gezari et al 2017;Yang et al 2017;Arcavi et al 2014;Holoien et al 2014Holoien et al , 2016Blagorodnova et al 2017a;Oknyansky et al 2019). As the referee of this paper pointed out, spectral variations on time scales of years have been observed amongst nearby AGNs (e.g NGC4151, NGC3516) since 1960s (Andrillat 1968;Tohline & Osterbrock 1976;Lyutyj et al 1984;Penston & Perez 1984).…”

Section: Introductionmentioning

confidence: 99%

Rapid “Turn-on” of Type-1 AGN in a Quiescent Early-type Galaxy SDSS1115+0544

Yan

Wang

Jiang

et al. 2019

ApJ

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We present a detailed study of a transient in the center of SDSS1115+0544 based on the extensive UV, optical, mid-IR light curves (LC) and spectra over 1200 days. The host galaxy is a quiescent early type galaxy at z = 0.0899 with a blackhole mass of 2 × 10 7 M . The transient underwent a 2.5 magnitude brightening over ∼ 120 days, reaching a peak V -band luminosity (extinction corrected) of −20.9 magnitude, then fading 0.5 magnitude over 200 days, settling into a plateau of > 600 days. Following the optical brightening are the significant mid-IR flares at 3.4 and 4.5µm, with a peak time delay of ∼ 180 days. The mid-IR LCs are explained as the echo of UV photons by a dust medium with a radius of 5 × 10 17 cm, consistent with E(B − V) of 0.58 inferred from the spectra. This event is very energetic with an extinction corrected L bol ∼ 4 × 10 44 erg s −1 . Optical spectra over 400 days in the plateau phase revealed newly formed broad Hα, β emission with a FWHM of ∼ 3750 km s −1 and narrow coronal lines such as [Fe VII], [Ne V]. This flare also has a steeply rising UV continuum, detected by multi-epoch Swift data at +700 to +900 days post optical peak. The broad Balmer lines and the UV continuum do not show significant temporal variations. The slow evolving LCs over 1200 days, the constant Balmer lines and UV continuum at late-times rule out TDE and SN IIn as the physical model for this event. We propose that this event is a "turn-on" AGN, transitioning from a quiescent state to a type 1 AGN with a sub-Eddington accretion rate of 0.017M /yr. This change occurred on a very short time scale of ∼ 120 − 200 days. The discovery of such a rapid "turn-on" AGN poses challenges to accretion disk theories and may indicate such event is not extremely rare.

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“…Cohen et al 1986;Storchi-Bergmann et al 1993;Eracleous & Halpern 2001 ;Denney et al 2014;Shappee et al 2014). With the repeated spectroscopic observations, the number of CL AGNs has increased rapidly in recent years MacLeod et al 2016MacLeod et al ,2019Yang et al 2018;Oknyansky et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Initial Results from a Systematic Search for Changing-look Active Galactic Nuclei Selected via Mid-infrared Variability

Sheng

Wang

Jiang

et al. 2020

ApJ

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Changing look active-galatic-nuclei (CL AGNs) can yield considerable insight into accretion physics as well as the co-evolution of black holes and their host galaxies. A large sample of these CL AGNs is essential to achieve the latter goal. We propose an effective method to select CL candidates from spectroscopic quasar catalogs using the mid-infrared (MIR) variability information derived from ALL-WISE/NEOWISE data releases. Our primary selection criteria include both a large amplitude flux variation and a transition of MIR color from an AGN to a normal galaxy. A pilot spectroscopic followup of 7 candidates among about 300 candidates selected from Sloan Digital Sky Survey low-redshift (z<0.5) AGN sample results in 6 new turn-off CL AGNs. We expect to obtain hundreds of CL AGNs once full spectroscopic follow-up of the sample is carried out.

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New changing look case in NGC 1566

Cited by 80 publications

References 42 publications

A flare in the optical spotted in the changing-look Seyfert NGC 3516

A flare in the optical spotted in the changing-look Seyfert NGC 3516

Rapid “Turn-on” of Type-1 AGN in a Quiescent Early-type Galaxy SDSS1115+0544

Initial Results from a Systematic Search for Changing-look Active Galactic Nuclei Selected via Mid-infrared Variability

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