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تسجيل مستخدم جديدLong-term optical monitoring of TeV emitting Blazars
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We present 10 years of R-band monitoring data of 31 northern blazars which were either detected at very high energy (VHE) gamma rays or listed as potential VHE gamma-ray emitters. The data comprise 11820 photometric data points in the R-band obtained in 2002-2012. We analyze the light curves by determining their power spectral density (PSD) slopes assuming a power-law dependence with a single slope $beta$ and a Gaussian probability density function (PDF). We use the multiple fragments variance function (MFVF) combined with a forward-casting approach and likelihood analysis to determine the slopes and perform extensive simulations to estimate the uncertainties of the derived slopes. We also look for periodic variations via Fourier analysis and quantify the false alarm probability through a large number of simulations. Comparing the obtained PSD slopes to values in the literature, we find the slopes in the radio band to be steeper than those in the optical and gamma rays. Our periodicity search yielded one target, Mrk 421, with a significant (p<5%) period. Finding one significant period among 31 targets is consistent with the expected false alarm rate, but the period found in Mrk~421 is very strong and deserves further consideration}.
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We present the results of photometric observations of three TeV blazars, 3C 66A, S5 0954+658 and BL Lacertae, during the period 2013--2017. Our extensive observations were performed in a total of 360 nights which produced $sim$6820 image frames in BV
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We present long term optical and near infrared flux variability analysis of 37 blazars detected in the $gamma$-ray band by the {it Fermi Gamma-Ray Space Telescope}. Among them, 30 are flat spectrum radio quasars (FSRQs) and 7 are BL Lac objects (BL L
acs). The photometric data in the optical (BVR) and infrared (JK) bands were from the Small and Moderate Aperture Research Telescope System acquired between 2008$-$2018. From cross-correlation analysis of the light curves at different wavelengths, we did not find significant time delays between variations at different wavelengths, except for three sources, namely PKS 1144$-$379, PKS B1424$-$418 and 3C 273. For the blazars with both B and J-band data, we found that in a majority of FSRQs and BL Lacs, the amplitude of variability ($sigma_m$) in the J-band is larger than B-band consistent with the dominance of the non-thermal jet over the thermal accretion disc component. Considering FSRQs and BL Lacs as a sample, there are indications of $sigma_m$ to increase gradually towards longer wavelengths in both, however, found to be statistically significant only between B and J-bands in FSRQs. In the B$-$J v/s J colour magnitude diagram, we noticed complicated spectral variability patterns. Most of the objects showed a redder when brighter (RWB) behaviour. Few objects showed a bluer when brighter (BWB) trend, while in some objects both BWB and RWB behaviours were noticed. These results on flux and colour characteristics indicate that the jet emission of FSRQs and BL Lacs is indistinguishable.
Optical observations of a sample of 12 $gamma$-ray bright blazars from four optical data archives, AAVSO, SMARTS, Catalina, and Steward Observatory, are compiled to create densely sampled light curves spanning more than a decade. As a part of the bla
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