Simultaneous [ITAL]UBVRI[/ITAL] Light Curves of the Seyfert Galaxy NGC 4151 during the Extraordinary Brightening from 1989 to 1996

Меркулова, Н. И.; Metik, L. P.; Pronik, I. I.

doi:10.1086/300830

Cited by 5 publications

(5 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Over 44 nights comprising 7 observational runs between 1993 March 22 and 1999 July 10 in each spectral band of Johnson's UBV RI system 672 measurements have been performed simultaneously through a circular aperture 15 in diameter. Observations of the nucleus of NGC 5548 were compared with analogous data samples of other Sy galaxies: NGC 4151 (Merkulova et al 1999), NGC 1275 (Pronik et al 1999a), and NGC 7469 (Merkulova 2000). The homogeneity of data obtained with the same telescope, using the same technique has made statistical comparison possible among different galaxies and different wave bands.…”

Section: Resultsmentioning

confidence: 99%

“…The following samples were used for the analysis: 1) Observations of the NGC 4151 nucleus obtained over 96 nights in 1989-1996. More than 1500 measurements were done simultaneously in each spectral band using the same technique as described in this paper (Merkulova et al 1999). The light curve of NGC 4151 in each of UBV RI bands shows a slow increase of intensity during almost the entire observation period, overlapped by rapid outbursts.…”

Section: Ubvri Light Curves Of Ngc 5548 In 1993-1999mentioning

confidence: 99%

See 1 more Smart Citation

UBVRI simultaneous observations of the nucleus of Seyfert galaxy NGC 5548 in 1993–1999

Меркулова

2002

A&A

Self Cite

View full text Add to dashboard Cite

Abstract. An ongoing program on photometric and spectral monitoring of some bright Seyfert galaxies has been carried out at the Crimean Astrophysical Observatory since 1989. Results of photometric observations of NGC 5548 obtained with the 1.25 m telescope are reported in this paper; it focuses on the analysis of intranight variations. During 44 observational nights in 1993-1999 in each spectral band of the Johnson UBV RI system, 672 measurements have been performed simultaneously through the round aperture (diameter 15 ) using differential photometry techniques. The estimated accuracy of each measurement is about 0.01 mag. The peak amplitude Rmax = Fmax/Fmin = 2.99 for the whole light curve was observed in the U band, while the minimum amplitude Fmax/Fmin = 1.37 occurred in the I band during the full observation period. UBV RI observations and good sampled data of international monitoring campaigns of NGC 5548, were used to calculate Structure Functions. A comparison is made of the characteristics of the long and short time scale variations of NGC 5548 with those of NGC 4151, NGC 7469 and NGC 1275. In order to examine the intranight variations of the nucleus of NGC 5548, standard deviations (SD) of the nightly averaged flux F , and a measure of intranight variability -SD/F were calculated for each night. Using this parameter, a probability characteristics is introduced, and duty cycles (the fraction of time when the galaxy is variable), characterizing the efficiency of the central energy source, were evaluated. It is concluded that intranight variability is really transient in character and manifests itself with different probabilities for different galaxies.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Ubvri Light Curves Of Ngc 5548 In 1993-1999mentioning

confidence: 99%

UBVRI simultaneous observations of the nucleus of Seyfert galaxy NGC 5548 in 1993–1999

Меркулова

2002

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…Kawaguchi et al 1998;Merkulova et al 1999;Cid Fernandes et al 2000;Collier & Peterson 2001;Doroshenko et al 2001 and many others). The SF of the first-order is defined as…”

Section: Structure Function Analysismentioning

confidence: 96%

Photometric activity of the Seyfert galaxy Markarian 6 from UBV observations in 1970–2001

Doroshenko

2003

A&A

View full text Add to dashboard Cite

The time where the SF for Mrk 6 reaches the upper plateau is about 3300 days. The observed SF can be interpreted by the superposition of independent flares model with the maximal duration of flares ∼800 days. If these flares are located in the radiation pressure dominated region of the accretion disk, the size of this region is about 70, 330 R S , assuming the viscous parameter α is 0.1, 0.01, respectively. It is concluded that the optical long-term variability of Seyfert galaxies can be explained by thermal instability in the accretion disk.

show abstract

“…The UBV RI light curves of NGC 4151 given by Merkulova et al (1999a) showed that the greatest amplitude of brightening of the nucleus in 1989-1996 was observed in the U band. The amplitude of flux variability of the NGC 4151 nucleus during the 7.3 years of our observations in an aperture D = 20 amounts to 2. m 2, 1. m 5, 0. m 9, 0. m 8 and 0. m 7 in the UBV RI bands, respectively.…”

Section: Extranight Variationsmentioning

confidence: 99%

“…The columns of this table show: (1) the number of periods of observation; (2) the starting and ending Julian Dates of the period of observations (JD = jd + 240 0000 days); (3) the duration of the observations dt, days; (4) the number of observational nights (n); (5) the number of measurements (n 1 ); (6) the power law spectral slopes of flux excesses for I-IV periods of the nucleus brightening (α pl ) according to Merkulova et al (1999a). Press (1978) suggested that the variability in quasars is caused by a process known as "noise".…”

Section: Log Of Characteristics Of Observational Datamentioning

confidence: 99%

Characteristics of the continuum variability of the nucleus of NGC 4151 in the optical from 1989-1996

Меркулова¹,

Metik²,

Pronik³

2001

A&A

Self Cite

View full text Add to dashboard Cite

Abstract. The Structure Function (SF) analysis of variable fluxes of the Seyfert galaxy NGC 4151 obtained during its extraordinary brightening in [1989][1990][1991][1992][1993][1994][1995][1996] in the UBV RI bands is reported. More than 1500 measurements were made in each spectral band. The logarithmic slopes of SF s for all samples of flux observations are found to be different for intranight and extranight flux variations: 0.81-0.96 and 0.44-0.60, respectively. The dependence of the SF slopes on the phase of nucleus activity was revealed. The SF slopes increased for intranight variations in accordance with the nucleus brightening and decreased for yearly variations. The processes causing the flux variations evolved during the nucleus brightening in different directions: for intranight variations the process evolved from flicker-noise to extreme shot-noise; for yearly variations -vice versa. The obtained data provide evidence in favor of the supposition that intranight and extranight variations are caused by different sources. As a result, the variable source of the NGC 4151 nucleus during the active phase in the UBV RI bands exhibited characteristics of radio loud AGNs. The highest values of logarithmic slopes of SF for variations on a time scale of years were in the range 0.8 ≤ b ≤ 1.1, and for 10-150 day flares they were as high as 2.2. There was flattening of the optical spectrum with increasing nucleus brightness. The brightness amplitude of the nucleus in the U band reduced to an aperture D = 5 over 7.3 years increased by a factor of more than 50. The brightness in the U band varied by a factor of more than 10 per year. The obtained characteristics of the variable source acting in the NGC 4151 nucleus from 1990-1996 do not contradict the model where the increasing nucleus brightening is caused by clouds of synchrotron radiation ejected from the nucleus during its active period.Key words. galaxies: NGC 4151 -Seyfert -active nuclei: optical variability IntroductionThe continuum variability search of active galactic nuclei (AGNs) is thought to be a useful probe for understanding their nature. Large international monitoring campaigns on some Seyfert galaxies (NGC 3783, NGC 4151, NGC 5548, NGC 7469) have produced a number of fundamental results which provide important constraints on models of the continuum source that cannot be obtained in a single observation. At present the most appropriate model is an accretion disk around a black hole.The program of simultaneous UBV RI monitoring of nuclei of Seyfert galaxies has been ongoing at the Crimean observatory since 1989. Some results important for the modelling of the AGNs have been obtained. Two types of intranight flares in the variable flux of the NGC 1275 nucleus were revealed by Pronik et al. (1999a, b) usingSend offprint requests to: N. Merkulova, e-mail: nelly@crao.crimea.ua 1982-1994 observations. Both types of intranight flares were independent of the nucleus brightness averaged by nights. It was supposed that intranight and extranight variations are ...

show abstract

Simultaneous [ITAL]UBVRI[/ITAL] Light Curves of the Seyfert Galaxy NGC 4151 during the Extraordinary Brightening from 1989 to 1996

Cited by 5 publications

References 20 publications

UBVRI simultaneous observations of the nucleus of Seyfert galaxy NGC 5548 in 1993–1999

UBVRI simultaneous observations of the nucleus of Seyfert galaxy NGC 5548 in 1993–1999

Photometric activity of the Seyfert galaxy Markarian 6 from UBV observations in 1970–2001

Characteristics of the continuum variability of the nucleus of NGC 4151 in the optical from 1989-1996

Contact Info

Product

Resources

About