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We present the results of the observational study of the blazar S5 0716+716 in the optical bands B, V, R, and I between March 2019 and August 2023 to investigate its variability on diverse time-scales. The blazar was followed up by the T60…

High Energy Astrophysical Phenomena · Physics 2024-07-15 Ergün Ege , Aykut Özdönmez , Aditi Agarwal , Tansel Ak

We analyzed the multi-band optical behaviour of the BL Lacertae object, S5 0716+714, during its outburst state from 2014 November - 2015 March. We took data on 23 nights at three observatories, one in India and two in Bulgaria, making…

High Energy Astrophysical Phenomena · Physics 2017-12-20 Aditi Agarwal , Alok C. Gupta , R. Bachev , A. Strigachev , E. Semkov , Paul J. Wiita , J. H. Fan , U. S. Pandey , S. Boeva , B. Spassov

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…

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 conducted a multi-wavelength monitoring campaign of the blazar S5 0716+714 from 2022 November 26 to 2023 May 28 using optical telescopes in Egypt and Bulgaria. Data were taken during 84 nights in 11 of which intranight monitoring was…

High Energy Astrophysical Phenomena · Physics 2025-07-03 B. M. Mihov , E. G. Elhosseiny , L. S. Slavcheva-Mihova , A. Takey , M. N. Ismail , R. Mawad

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 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

We present our optical photometric observations of three TeV blazars, PKS 1510-089, PG 1553+113 and Mrk 501 taken using two telescopes in India, one in Bulgaria, one in Greece and one in Serbia during 2012 - 2014. These observations covered…

High Energy Astrophysical Phenomena · Physics 2016-02-24 Alok C. Gupta , A. Agarwal , J. Bhagwan , A. Strigachev , R. Bachev , E. Semkov , H. Gaur , G. Damljanovic , O. Vince , Paul J. Wiita

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 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 continuously monitored the blazar S5 0716+714 in the optical $g$, $r$ and $i$ bands from Nov. 10, 2017 to Jun. 06, 2019. The total number of observations is 201 nights including 26973 data points. This is a very large quasi-simultaneous…

High Energy Astrophysical Phenomena · Physics 2020-04-01 Dingrong Xiong , Jinming Bai , Junhui Fan , Dahai Yan , Minfeng Gu , Xuliang Fan , Jirong Mao , Nan Ding , Rui Xue , Weimin Yi

We present results of our intra-night optical flux monitoring observations of S5 0716+714 done simultaneously in gRI filters. The observations were done using Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME)…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 C. S. Stalin , K. S. Kawabata , M. Uemura , M. Yoshida , N. Kawai , K. Yanagisawa , Y. Shimizu , D. Kuroda , S. Nagayama , H. Toda

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

We report the first extensive optical flux and spectral variability study of the TeV blazar TXS 0506+056 on intra-night to long-term timescales using BVRI data collected over 220 nights between January 21, 2017 to April 9, 2022 using 8…

We report results of multiband optical monitoring of two well known blazars, S5 0716+714 and BL Lacertae, carried out in 1996 and 2000-01 with an aim to study optical variations on time scales from minutes to hours and longer.The light…

Astrophysics · Physics 2007-05-23 C. S. Stalin , Gopal-Krishna , Ram Sagar , Paul J. Wiita , V. Mohan , A. K. Pandey

To search for optical variability on a wide range of timescales, we have carried out photometric monitoring of 3C 454.3, 3C 279 and S5 0716+714. CCD magnitudes in B, V, R and I pass-bands were determined for $\sim$ 7000 new optical…

High Energy Astrophysical Phenomena · Physics 2017-12-20 A. Agarwal , A. C. Gupta

We report rapid optical variability for the blazar S5 0716+71 during 2010 March 08-10 & 19-20 in the CCD observations made from Mt.Abu Infrared Observatory. The light curves are constructed for the duration longer than 3-hours each night,…

High Energy Astrophysical Phenomena · Physics 2011-05-04 Sunil Chandra , K. S. Baliyan , S. Ganesh , U. C. Joshi

We have monitored the flat spectrum radio quasar, 3C 279, in the optical $B$, $V$, $R$ and $I$ passbands from 2018 February to 2018 July for 24 nights, with a total of 716 frames, to study flux, colour and spectral variability on diverse…

We present the results of multiband observations of the blazar S5 0716+714 intra-night variability performed during 23 nights in the period from 04.2014 through 04.2015. The bluer-when-brighter trend is detected in both intra- and…

Astrophysics of Galaxies · Physics 2021-03-17 Marina S. Butuzova

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
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