Optical Monitoring of Ngc4151 During 110 Years

Oknyanskij, V. L.; Metlova, N. V.; Huseynov, N.; Guo, Dadong; Lyuty, V. M.

doi:10.18524/1810-4215.2016.29.85058

Cited by 23 publications

(39 citation statements)

References 3 publications

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“…Only for one object, GQ Comae, do we see difference at about a factor of three between lags in the L and K bands. A similar difference was seen for NGC 4151 but only during the long, very high state which was the only one during last 110 years (Oknyanskij et al 2013). The probability of observing an object exactly in its highest state is not large.…”

Section: Introductionsupporting

confidence: 74%

“…At the same time it was first shown (Oknyanskij 1999(Oknyanskij , 2002Oknyanskij & Horne 2001) that for a number of AGNs the time delay of variability (in the K band) depends on the UV luminosity as τ ∝ L 1/2 U V in accordance with the theoretical result of Barvainis (1987Barvainis ( , 1992. In the recent publications Yoshii et al (2014) and Hönig (2014) considered in detail the possibility of estimating cosmological parameters on the basis of measuring the dust sublimation radii in AGNs.…”

Section: Cosmological Applicationsmentioning

confidence: 54%

“…The ability to measure cosmological constants using the time delays of the near-infrared variability relative to the optical one was first mentioned by Kobayashi et al (1998) and independently by Oknyanskij (1999Oknyanskij ( , 2002. At the same time it was first shown (Oknyanskij 1999(Oknyanskij , 2002Oknyanskij & Horne 2001) that for a number of AGNs the time delay of variability (in the K band) depends on the UV luminosity as τ ∝ L 1/2 U V in accordance with the theoretical result of Barvainis (1987Barvainis ( , 1992.…”

Section: Cosmological Applicationsmentioning

confidence: 59%

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The Relative Wavelength Independence of Ir Lags in Active Galactic Nuclei: Implications for the Distribution of the Hot Dust

Gaskell

Shimanovskaya

2015

OAP

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ABSTRACT. We show that, contrary to simple predictions, most AGNs show at best only a small increase of lags in the J, H, K, and L bands with increasing wavelength. We suggest that a possible cause of this near simultaneity of the variability from the near-IR to the mid-IR is that the hot dust is in a hollow bi-conical outflow of which we only see the near side. Although most AGNs show near simultaneity of IR variability, there was at least one epoch when NGC 4151 showed the sharply increasing IR lag with the increase of the wavelength. This behaviour might also be present in GQ Comae. We discuss these results briefly. The relative wavelength independence of IR lags simplifies the use of IR lags for estimating cosmological parameters.

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Section: Introductionsupporting

confidence: 74%

Section: Cosmological Applicationsmentioning

confidence: 54%

Section: Cosmological Applicationsmentioning

confidence: 59%

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The Relative Wavelength Independence of Ir Lags in Active Galactic Nuclei: Implications for the Distribution of the Hot Dust

Gaskell

Shimanovskaya

2015

OAP

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“…Sillanpaa et al 1988;Lehto & Valtonen 1996;Fan et al 1998;Rieger & Mannheim 2000;Valtaoja et al 2000;De Paolis et al 2003;Sudou et al 2003;Guo et al 2006;Gezari et al 2007;Guo et al 2014;Liu et al 2015;Bon et al 2012;Graham et al 2015a,b;Shapovalova et al 2016). 100 years [e.g., NGC 4151, from 1906(Oknyanskij & Lyuty 2007, 3C273, from the 1880s (Smith & Hoffleit 1963), and OJ287, from 1891 (Valtonen & Sillanpää 2011) to the present. Therefore, well-covered long-term lightcurves of nearby AGN are required to search for the presence or absence of periodic signatures.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Periodicity in 43 Year-Long Monitoring of NGC 5548

Bon¹,

Zucker²,

Netzer³

et al. 2016

ApJS

113

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We present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 Hβ spectra and analyzed the long-term spectral variations of the 5100Å continuum and the Hβ line. Our analysis is based on standard procedures, including the LombScargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a -2 -∼5700 day periodicity in the continuum light curve, the Hβ light curve, and the radial velocity curve of the red wing of the Hβ line. The data are consistent with orbital motion inside the broad emission line region of the source. We discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk.

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“…It would be interesting to know if this is quasi-periodic. The possibility of quasi-periodical variability has been discussed for some other well-known CL AGNs such as NGC 4151 [14] and NGC 5548 [15]. Such type cyclical periodicity is expected for TDEs [16] or tidal stars stripping [17,18].…”

Section: Monitoring Of the Typical CL Object Ngc 2617mentioning

confidence: 99%

Changing-look Narrow-Line Seyfert 1s?

Malanchev¹,

Gaskell²

2018

Proceedings of Revisiting Narrow-Line Seyfert 1 Galaxies and Their Place in the Universe — PoS(NLS1-2018)

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Two major challenges to unification schemes for active galactic nuclei (AGN) are the existence of Narrow-Line Seyfert 1s (NLS1s) and the existence of changing-look (CL) AGNs. AGNs can drastically change their spectral appearance in the optical (changing their Seyfert type) and/or in the X-ray region. We illustrate the CL phenomenon with our multi-wavelength monitoring of NGC 2617 and discuss its properties compared with NLS1s. There are few examples of CL NLS1s and the changes are mostly only in the X-ray region. It has been proposed that some of these could be cases of a tidal-disruption events (TDE) or supernova events. If BLRs have a flat geometry and NLS1s are seen face-on then we have to see CL cases only if the orientation of the BLR changes as a result of a TDE or a close encounter of a star without a TDE. If NLS1s include both high Eddington accretion rate and low-inclination AGNs then a significant fraction of NLS1s could be obscured and would not be identified as NLS1s. CL cases might happen more in such objects if dust sublimation occurs following a strong increase in the optical luminosity.Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe -NLS1 Padova

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Optical Monitoring of Ngc4151 During 110 Years

Cited by 23 publications

References 3 publications

The Relative Wavelength Independence of Ir Lags in Active Galactic Nuclei: Implications for the Distribution of the Hot Dust

The Relative Wavelength Independence of Ir Lags in Active Galactic Nuclei: Implications for the Distribution of the Hot Dust

Evidence for Periodicity in 43 Year-Long Monitoring of NGC 5548

Changing-look Narrow-Line Seyfert 1s?

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