24 citations · 73 across the 18 of their papers we have counts for
19 papers
Gamma-ray Quasi-periodic Oscillations in the Changing Look Blazar B2 1420+326 (OQ 334)
Sunanda, Shubham Kishore, Alok C. Gupta
In the Fermi-LAT gamma-ray light curve from January 1 to August 25, 2026, of the changing look blazar B2 1420+326, we report here the detection of transient quasi-periodic oscillat…
Revisiting neutrino event epochs for the blazar PKS 0735+178 with TESS
Shubham Kishore, Alok C. Gupta, Debanjan Bose
We present here the results of the optical light curve variability analysis of the blazars PKS 0735+178, in weeks-scale flare state, observed in three sectors with the Transiting E…
Detection of Quasiperiodic Oscillations in the Blazar PKS 0735+178 with TESS
Shubham Kishore, Alok C. Gupta, Paul J. Wiita +2
We report here the detection of signatures of a quasiperiodic oscillation (QPO) and a short flare in the optical light curve of the blazar PKS 0735+178, observed in two sectors, 71…
Multi-band optical photometric variability of the blazar OJ 287 from 2015 to 2025
Alok C. Gupta, Karan Dogra, Mark Kidger +101
We present the most densely sampled multi-band optical photometric observations of the peculiar BL Lacertae object OJ 287 from 2015 to 2025 with a focus on its optical activity on…
Detection of optical quasi-periodic oscillation in the blazar 3C 454.3
Karan Dogra, Alok C. Gupta, C. M. Raiteri +83
We analyzed 19 years of -band data of the blazar 3C 454.3 from the Whole Earth Blazar Telescope (WEBT) archive, along with new data from its members and from public archives suc…
Detection of quasi-periodic oscillations in the 37 GHz radio light curve of the blazar Ton 599 during 1990-2020
Alok C. Gupta, Alexandr E. Volvach, Shubham Kishore +6
Blazars are a subclass of radio-loud active galactic nuclei (AGNs) that display strong multi-wavelength variability on diverse timescales ranging from years down to minutes. In the…
Variability Study and Searching for QPOs with day-like periods in the blazar S5 0716+714 with TESS
Shubham Kishore, Alok C. Gupta, Paul J. Wiita
Using an unprecedented cadence of 30 minutes provided by the Transiting Exoplanet Survey Satellite (TESS), we have examined the optical light curves (LCs) of the blazar S5 0716+714…
Possibility of Month-scale Quasi-periodic Oscillations in the Gamma-ray Light Curve of OP 313
Sandeep Kumar Mondal, Shubham Kishore, Alok C. Gupta +1
In this work, we report evidence suggesting the potential future detection of a month-scale quasi-periodic oscillation (QPO) in the gamma-ray light curve of OP 313. We analysed alm…
Identifying the secondary jet in the RadioAstron image of OJ~287
Mauri J. Valtonen, Lankeswar Dey, Staszek Zola +26
The 136 year long optical light curve of OJ~287 is explained by a binary black hole model where the secondary is in a 12 year orbit around the primary. Impacts of the secondary on…
Multi-band optical variability of the blazar OP 313 in the outburst state during 2024-2025
P. U. Devanand, Alok C. Gupta, Karan Dogra +2
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 nigh…
Evidence of jet activity from the secondary black hole in the OJ287 binary system
Mauri J. Valtonen, Staszek Zola, Alok C. Gupta +29
We report the study of a huge optical intraday flare on November 12, 2021, at 2 am UT, in the blazar OJ287. In the binary black hole model it is associated with an impact of the se…
Optical Continuum Reverberation Mapping of a Candidate IMBH in a Nearby Seyfert 1 Galaxy
Wenwen Zuo, Hengxiao Guo, Jingbo Sun +25
To investigate the short-term variability and determine the size of the optical continuum emitting region of intermediate-mass black holes (IMBHs), we carried out high-cadence, mul…
Rapid Optical Flare in the Extreme TeV Blazar 1ES 0229+200 on Intraday Timescale with TESS
Shubham Kishore, Alok C. Gupta, Paul J. Wiita +1
The extreme TeV blazar 1ES 0229+200 is a high-frequency-peaked BL Lacertae object. It has not shown intraday variability in extensive optical and X-ray observations. Nor has it sho…
Optical intra-day variability of the blazar S5 0716+714
Tushar Tripathi, Alok C. Gupta, Ali Takey +18
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 i…
Rapid Optical Flares in the Blazar OJ 287 on Intraday Timescales with TESS
Shubham Kishore, Alok C. Gupta, Paul J. Wiita
We have analyzed the optical light curves of the blazar OJ 287 obtained with the Transiting Exoplanet Survey Satellite (TESS) over about 80 days from 2021 October 13 to December 31…
Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and -ray brightness levels
C. M. Raiteri, M. Villata, M. I. Carnerero +64
In 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and -ray bands. We present optical photometri…
Intra-night optical flux and polarization variability of BL~Lacertae during its 2020 2021 high state
Rumen Bachev, Tushar Tripathi, Alok C. Gupta +15
In this work, we report the presence of rapid intra-night optical variations in both -- flux and polarization of the blazar BL Lacertae during its unprecedented 2020--2021 high sta…
The optical behaviour of BL Lacertae at its maximum brightness levels: a blend of geometry and energetics
C. M. Raiteri, M. Villata, S. G. Jorstad +13
In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical…
Detection of Quasi-Periodic Oscillations in the Blazar S4 0954+658 with TESS
Shubham Kishore, Alok C. Gupta, Paul J. Wiita
We report the detection of several quasi-periodicities around 0.6--2.5 days in the optical emission of the blazar S4 0954+658. The source was observed by the Transiting Exoplanet S…