Spectral Variability of Six Bright Bl Lac Objects in the Near IR

The results of several photometric campaigns (1986–1993) in the near IR of the six bright BL Lac objects 3C 66A, PKS 0422+004, PKS 0735+178, PKS 0754+100, PKS 0829+046 and OQ 530 are presented. The observations were carried out at the 1.5 m Italian IR Telescope at Gornergrat (TIRGO − 3150 m a.s.l.) equipped with a IR photometer using a InSb detector cooled at the solid nitrogen temperature and the standard J, H, K filters. The principal aims of our program are the search of rapid variability (typical time scales of 1 day or less) and of correlations between the flux level (typically in the J band, where the largest variation amplitude is found) and the spectral slope. In the following we summarize some relevant results.

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Spectral Variability of BL Lac Objects

Publications of the Astronomical Society of Australia ◽

10.1071/as01113 ◽

2002 ◽

Vol 19 (1) ◽

pp. 111-113 ◽

Cited By ~ 21

Author(s):

R. D'Amicis ◽

R. Nesci ◽

E. Massaro ◽

M. Maesano ◽

F. Montagni ◽

...

Keyword(s):

The Other ◽

Time Interval ◽

Spectral Slope ◽

Spectral Variability ◽

Bl Lac Objects ◽

Bl Lacertae ◽

Bl Lac

AbstractWe present the relation between optical luminosity and spectral slope for eight BL Lac objects (3C66A, PKS 0422+00, S5 0716+71, OJ 287, ON 231, OQ 530, S5 1803+78 and BL Lacertae), derived from B, V, R, and I observations spanning a time interval of about 5 years. Four objects show a marked correlation between spectral slope and luminosity, being bluer when brighter, while for the other four the correlation is weaker or absent. Possible explanations are briefly discussed in the framework of current models of the BL Lac phenomenon.

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Spectral Variability of Six Bright BL Lac Objects in the Near IR

Multi-Wavelength Continuum Emission of AGN ◽

10.1007/978-94-010-9537-2_114 ◽

1994 ◽

pp. 400-400

Author(s):

E. Massaro ◽

R. Nesci ◽

G. C. Perola ◽

D. Lorenzetti ◽

L. Spinoglio

Keyword(s):

Spectral Variability ◽

Bl Lac Objects ◽

Near Ir ◽

Bl Lac

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Serendipitous VLBI Observations of Intraday Variability in the BL Lac Objects 1334–127, 2131–021, and 2155–152

International Astronomical Union Colloquium ◽

10.1017/s0252921100045528 ◽

1998 ◽

Vol 164 ◽

pp. 273-274

Author(s):

P. Yu. Kochanev ◽

D. C. Gabuzda

Keyword(s):

Rapid Variability ◽

Bl Lac Objects ◽

Polarization Structure ◽

Vlbi Observations ◽

Bl Lac ◽

Vlbi Data ◽

Intraday Variability

AbstractGlobal λ = 6 cm VLBI polarization observations of intraday variability in the three BLLacertae objects 1334–127, 2131–021, and 2155–152 are analyzed. Integrated VLA measurements during the VLBI observations show that although there were no substantial total intensity variations, the polarizations for these three sources varied significantly during the VLBI experiment. The VLBI data were divided into 2-3 hour segments in order to search for corresponding rapid variability in the VLBI polarization structure. Our analysis shows that the VLA polarization variability in 2155–152 and 2131–021 is present in the VLBI data (i.e., it occurred on mas scales), but this is not the case for 1334–127.

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Optical Microvariability in Complete Samples of BL Lac Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900175825 ◽

1994 ◽

Vol 159 ◽

pp. 393-393

Author(s):

Jochen Heidt

Keyword(s):

Time Scales ◽

Duty Cycle ◽

Ccd Photometry ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac

A radio-selected (1 Jy, Stickel et al., 1991) and a x-ray selected (EXOSAT, Giommi et al., 1991) sample of BL Lac objects was monitored by performing relative CCD photometry in order to examine the duty cycle, the dominant time-scales and the typical amplitudes of the variability. The samples consist of 34 and 11 objects, respectively.

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Long term γ-ray variability of blazars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936769 ◽

2020 ◽

Vol 634 ◽

pp. A80 ◽

Cited By ~ 2

Author(s):

Bhoomika Rajput ◽

C. S. Stalin ◽

Suvendu Rakshit

Keyword(s):

Time Scales ◽

Gamma Ray ◽

Spectral Energy Distribution ◽

Broad Band ◽

Spectral Energy ◽

Bl Lac Objects ◽

Spectrum Radio ◽

Bl Lac ◽

Bl Lacs

We used the data from the Fermi Gamma-ray Space Telescope to characterise the γ-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars (FSRQs) and 639 are BL Lac objects (BL Lacs). We generated monthly binned light curves of our sample for a period of approximately nine years from 2008 August to 2017 December and quantified variability by using excess variance (Fvar). On month-like time scales, 371/481 FSRQs are variable (80%), while only about 50% (304/639) of BL Lacs are variable. This suggests that FSRQs are more variable than BL Lac objects. We find a mean Fvar of 0.55 ± 0.33 and 0.47 ± 0.29 for FSRQs and BL Lacs respectively. Large Fvar in FSRQs is also confirmed from the analysis of the ensemble structure function. By Dividing our sample of blazars based on the position of the synchrotron peak in their broad-band spectral energy distribution, we find that the low synchrotron peaked (LSP) sources have the largest mean Fvar value of 0.54 ± 0.32 while the intermediate synchrotron peaked (ISP) and high synchrotron peaked sources have mean Fvar values of 0.45 ± 0.25 and 0.47 ± 0.33 respectively. On month-like time scales, we find FSRQs to show a high duty cycle (DC) of variability of 66% relative to BL Lacs that show a DC of 36%. We find that both the Fvar and time scale of variability (τ) do not correlate with MBH. We note that Fvar is found to be weakly correlated with Doppler factor (δ) and τ is also weakly correlated with δ. Most of the sources in our sample have τ of the order of days, which might be related to processes in the jet. We find marginal difference in the distribution of τ between FSRQs and BL Lacs.

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X-Ray Spectral Variability of BL Lac Objects

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1984.tb23392.x ◽

1984 ◽

Vol 422 (1 Eleventh Texa) ◽

pp. 367-367

Author(s):

DARIO MACCAGNI ◽

TOMMASO MACCACARO ◽

MASSIMO TARENGHI

Keyword(s):

Spectral Variability ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac

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Optical variability of X-ray selected blazars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307005649 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 399-400 ◽

Cited By ~ 2

Author(s):

Omar M. Kurtanidze ◽

Maria G. Nikolashvili ◽

Givi N. Kimeridze ◽

Lorand A. Sigua ◽

Bidzina Z. Kapanadze

Keyword(s):

Time Scales ◽

Significant Variation ◽

Optical Variability ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac ◽

Long Time

AbstractWe present optical R band photometry of nine X-ray selected BL Lac objects: 1ES 0229+200, 1ES 0323+022, 1ES 502+675, 1ES 0647+250, 1ES 0806+524, 1ES0927+500, 1ES 1028+511, 1ES 1959+650, 1ES2344+514.Variability on long time scales within one magnitude in R band was found for all of the observed objects, except 1ES 0229+200 and 1ES0927+500. Largest variation was detected for 1ES 0502+675 and equals to 1.07 mag. Only few objects show statistically significant variation on intra-day scale.

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Arcsecond Scale Polarization of BL Lac Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900080001 ◽

1996 ◽

Vol 175 ◽

pp. 55-56

Author(s):

C. Stanghellini ◽

P. Cassaro ◽

M. Bondi ◽

D. Dallacasa ◽

R. Della Ceca ◽

...

Keyword(s):

Galactic Nuclei ◽

Radio Galaxies ◽

Radio Spectrum ◽

Line Of Sight ◽

Parent Population ◽

Rapid Variability ◽

Bl Lac Objects ◽

Relativistic Jet ◽

Bl Lac ◽

Optical Continuum

BL Lac objects are an enigmatic class of active galactic nuclei. They are characterized by high luminosity, a flat radio spectrum that steepens at higher energies, relatively high optical and radio polarization, rapid variability and an optical continuum with weak or absent emission lines (see Urry and Padovani, 1995 for a recent review).These properties have been interpreted in terms of a relativistic jet closely aligned to the line of sight (Blandford and Rees, 1978, Ghisellini et al., 1993). This model, known as the beaming model, implies that there must be a so called “parent population” of radio sources intrinsically identical to BL Lac objects, but with the jets oriented at large angles to the line of sight. Browne (1983) was the first to propose the low luminosity FR I radio galaxies as the most likely candidates for the “parent population” of the core dominated BL Lac objects. An outcome of the beaming model is that all the properties not depending on orientation should be shared by the BL Lac objects and the FR I radio galaxies.

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