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We present the results of variability power spectral density (PSD) analysis using multiwavelength radio to GeV\,$\gamma$-ray light curves covering decades/years to days/minutes timescales for the blazars 3C 279 and PKS 1510-089. The PSDs…

We present the results of the power spectral density (PSD) analysis for the blazars Mrk\,421 and PKS\,2155$-$304, using good-quality, densely sampled light curves at multiple frequencies, covering 17 decades of the electromagnetic spectrum,…

High Energy Astrophysical Phenomena · Physics 2020-04-22 Arti Goyal

We present a study of high-cadence, high-precision, optical light curves from the TESS satellite of 67 blazars in the southern sky. We provide descriptive flux statistics, power spectral density model parameters, and characteristic…

High Energy Astrophysical Phenomena · Physics 2024-06-18 Ryne Dingler , Krista Lynne Smith

Characteristic variability timescales in blazar gamma-ray light curves can provide insight into the physical processes responsible for the gamma-ray variability. The power spectral density (PSD) is capable of revealing such timescales,…

High Energy Astrophysical Phenomena · Physics 2019-11-06 James L. Ryan , Aneta Siemiginowska , Malgosia Sobolewska , Jonathan Grindlay

We present X-ray intraday variability and power spectral density (PSD) analyses of the longest 23 pointed XMM-Newton observations of the blazar 3C 273 that were taken during 2000 -- 2021. These good time intervals contained between 5 and…

High Energy Astrophysical Phenomena · Physics 2022-02-23 G. S. Pavana Gowtami , Haritma Gaur , Alok C. Gupta , Paul J. Wiita , Mai Liao , Martin Ward

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 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 results of our power spectral analysis for the BL Lac object PKS 0735+178 utilizing the Fermi-LAT survey at high-energy $\gamma$-rays, several ground-based optical telescopes, and single-dish radio telescopes operating at GHz…

High Energy Astrophysical Phenomena · Physics 2017-03-22 Arti Goyal , Lukasz Stawarz , Michal Ostrowski , Valeri Larionov , Gopal-Krishna , Paul J. Wiita , Santosh Joshi , Marian Soida , Ivan Agudo

We present the results of the \textit{Fermi}-LAT 10-years-long light curves (LCs) modeling of selected blazars: six flat spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs), examined in 7-, 10-, and 14-day binning. The LCs and…

High Energy Astrophysical Phenomena · Physics 2021-09-24 Mariusz Tarnopolski , Natalia Żywucka , Volodymyr Marchenko , Javier Pascual-Granado

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

We have carried out optical (R band) intraday variability (IDV) monitoring of a sample of ten bright low energy peaked blazars (LBLs). Forty photometric observations, of an average of ~ 4 hours each, were made between 2008 September and…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Bindu Rani , Alok C. Gupta , U. C. Joshi , S. Ganesh , Paul J. Wiita

In an optical monitoring program to characterize the variability properties of blazar, we observed 10 sources from the Roma-BZCAT catalogue for 26 nights in V and R bands during October 2014 to June 2015 with two telescopes located in…

High Energy Astrophysical Phenomena · Physics 2021-12-08 Nibedita Kalita , Alok C. Gupta , Minfeng Gu

Aims: The optical variability of the blazar PKS 2155-304 is investigated to characterise the red noise behaviour at largely different time scales from 20 days to O(>10 yrs). Methods: The long-term optical light curve of PKS 2155-304 is…

High Energy Astrophysical Phenomena · Physics 2011-08-08 Max A. Kastendieck , Michael C. B. Ashley , Dieter Horns

The power spectral density (PSD) represents a key property quantifying the stochastic or random noise type fluctuations in variable sources like Active Galactic Nuclei (AGN). In recent years, estimates of the PSD have been refined by…

High Energy Astrophysical Phenomena · Physics 2020-10-05 Nachiketa Chakraborty , Frank M. Rieger

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

Context. We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155-304, W Comae, and of the flat spectrum radio quasar PKS 1510-089, as a part of a photometric monitoring program in the…

High Energy Astrophysical Phenomena · Physics 2015-06-16 Angela Sandrinelli , Stefano Covino , Aldo Treves

We analyze X-ray light curves of the blazars Mrk 421, PKS 2155-304, and 3C 273 using observations by the Soft X-ray Telescope on board AstroSat and archival XMM-Newton data. We use light curves of length 30-90 ks each from 3-4 epochs for…

High Energy Astrophysical Phenomena · Physics 2023-10-27 Joy Bhattacharyya , Ritesh Ghosh , Ritaban Chatterjee , Nabanita Das

The X-ray emission from blazars has been widely investigated using several space telescopes. In this work, we explored statistical properties of the X-ray variability in the blazars S5 0716+714, OJ 287, Mkn 501 and RBS 2070 using the…

We report the flux and spectral variability of PG 1553+113 on intra-night (IDV) to short-term timescales using BVRI data collected over 91 nights from 28 February to 8 November 2019 employing ten optical telescopes: three in Bulgaria, two…

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