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We report the results of optical monitoring for a sample of 11 blazars including 10 BL Lacs and 1 Flat Spectrum Radio Quasar (FSRQ). We have measured the multiband optical flux and colour variations in these blazars on intra-day and…

High Energy Astrophysical Phenomena · Physics 2013-11-21 Haritma Gaur , Alok C. Gupta , A. Strigachev , R. Bachev , E. Semkov , Paul J. Wiita , S. Peneva , S. Boeva , L. Slavcheva-Mihova , B. Mihov , G. Latev , U. S. Pandey

We present the results obtained from our campaign to characterize the intra-night-optical variability properties of blazars detected by the {\it Fermi} Large Area Telescope. This involves R-band monitoring observations of a sample of 18…

High Energy Astrophysical Phenomena · Physics 2022-02-16 K. Subbu Ulaganatha Pandian , A. Natarajan , C. S. Stalin , Ashwani Pandey , S. Muneer , B. Natarajan

We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during October and November 2014 including quasi-simultaneous observations in V and R bands using two optical telescopes in India. We have studied multi-band optical…

Astrophysics of Galaxies · Physics 2015-06-02 Aditi Agarwal , Alok C. Gupta

We present the analysis results of flux and spectral variability of the blazar OP 313 across intra-night to short-term timescales using BVRI photometric data, gathered over 25 nights from Nov 2024 to May 2025, using two optical telescopes…

High Energy Astrophysical Phenomena · Physics 2025-09-11 P. U. Devanand , Alok C. Gupta , Karan Dogra , Shubham Kishore , Tushar Tripathi

We present the observational results of multi-colour optical monitoring of eight red blazars from 2003 September to 2004 February. The aim of our monitoring is to investigate the spectral variability as well as the flux variations at short…

Astrophysics · Physics 2009-11-11 Minfeng Gu , C. -U. Lee , Soojong Pak , H. S. Yim , A. B. Fletcher

The long-term optical and infrared color variability of blazars has been investigated with the SMARTS monitoring data. The sample in this study consists of 49 flat spectrum radio quasars and 22 BL Lac objects. The fractional variability…

Astrophysics of Galaxies · Physics 2015-11-11 Bing-Kai Zhang , Xiao-Shan Zhou , Xiao-Yun Zhao , Ben-Zhong Dai

We carried out multi-color optical monitoring of a sample of ten blazars from 2005 to 2011. The sample contains 3 LBLs, 2 IBLs, 4 HBLs, and 1 FSRQ. Our monitoring focused on the long-term variability and the sample included nine BL Lac…

Astrophysics of Galaxies · Physics 2018-08-08 Nankun Meng , Xiaoyuan Zhang , Jianghua Wu , Jun Ma , Xu Zhou

In this work, we present the results of our multi-band microvariability study of the famous blazar BL Lac. We performed microvariablity observations of the source in the optical VRI bands for 4 nights in the year 2016. We studied the…

High Energy Astrophysical Phenomena · Physics 2017-11-27 Gopal Bhatta , James R. Webb

To search for optical variability on a wide range of timescales, we have carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhibiting remarkably…

We present an extensive recent multi-band optical photometric observations of the blazar S5 0716+714 carried out over 53 nights with two telescopes in India, two in Bulgaria, one in Serbia, and one in Egypt during 2019 November -- 2022…

We monitored BL Lacertae frequently during 2014 - 2016 when it was generally in a high state. We searched for intra-day variability for 43 nights using quasi-simultaneous measurements in the B, V, R, and I bands (totaling 143 light curves);…

High Energy Astrophysical Phenomena · Physics 2017-12-20 Haritma Gaur , Alok C. Gupta , R. Bachev , A. Strigachev , E. Semkov , Paul J. Wiita , M. F. Gu , S. Ibryamov

We used the data from the Fermi Gamma-ray Space Telescope to characterise the {\gamma}-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…

High Energy Astrophysical Phenomena · Physics 2020-02-12 Bhoomika Rajput , C. S. Stalin , Suvendu Rakshit

We investigate the temporal and colour variability of 897 blazars, comprising 455 BL Lacertae objects (BL Lacs) and 442 Flat Spectrum Radio Quasars (FSRQs), selected from the Roma-BZCAT catalogue, using the multi-band light curves from the…

Astrophysics of Galaxies · Physics 2021-12-22 Vibhore Negi , Ravi Joshi , Krishan Chand , Hum Chand , Paul Wiita , Luis C. Ho , Ravi S. Singh

We have measured multi-band optical flux and colour variations for a sample of 12 low energy peaked blazars on short, day-to-month, timescales. Our sample contains six BL Lacertae objects and six flat spectrum radio quasars. These…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Bindu Rani , Alok C. Gupta , A. Strigachev , R. Bachev , Paul J. Wiita , E. Semkov , E. Ovcharov , B. Mihov , S. Boeva , S. Peneva , B. Spassov , S. Tsvetkova , K. Stoyanov , A. Valcheva

In this presentation, we report the results of intraday variability in the optical (BVRI bands) and hard X-ray band (3-79 keV) in a number of blazars. In the optical microvariability studies of the blazars S5 0716+714 and BL Lac, we…

High Energy Astrophysical Phenomena · Physics 2022-10-18 Gopal Bhatta

Blazars are the established sources of an intense and variable non-thermal radiation extending from radio wavelengths up to HE and VHE gamma-rays. Understanding the spectral evolution of blazars in selected frequency ranges, as well as…

High Energy Astrophysical Phenomena · Physics 2014-12-24 Alicja Wierzcholska , Michał Ostrowski , Łukasz Stawarz , Stefan Wagner , Marcus Hauser

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…

High Energy Astrophysical Phenomena · Physics 2020-08-28 P. Z. Safna , C. S. Stalin , Suvendu Rakshit , Blesson Mathew

In this study, we analyze the $\sim 16$ yr Fermi-LAT data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae type objects (BL Lacs), and 4 blazar candidates of unknown type objects (BCU), and exhibit their…

High Energy Astrophysical Phenomena · Physics 2025-01-22 Junhao Deng , Yunguo Jiang

We report the first study to characterise intranight variability of the blazar class from the perspective of (rest-frame) UV emission. For this, we carried out intranight optical monitoring of 14 flat-spectrum radio quasars (FSRQs) located…

Astrophysics of Galaxies · Physics 2022-01-02 Krishan Chand , Gopal-Krishna , Amitesh Omar , Hum Chand , Sapna Mishra , P. S. Bisht , S. Britzen

Blazars, the peculiar class of active galactic nuclei (AGN), are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across…

High Energy Astrophysical Phenomena · Physics 2024-08-13 M. Reshma , Aditi Agarwal , C. S. Stalin , Prajwel Joseph , Akanksha Dagore , Amit Kumar Mandal , Ashish Devaraj , S. B. Gudennavar
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