53 citations · 902 across the 48 of their papers we have counts for
49 papers
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…
Multiband optical variability on diverse timescales of the blazar Ton 599 from 2011 to 2023
O. Vince, C. M. Raiteri, M. Villata +72
(Shortened)Context: We analyze the optical variability of the FSRQ Ton 599 using BVRI photometry from the WEBT collaboration (2011-2023), complemented by photometric and spectrosco…
VHE FSRQs with Fermi-LAT: VHE and even brighter states in high-z FSRQs due to an HBL-like component?
Megha, Pankaj Kushwaha
Very high-energy (VHE) detected flat-spectrum radio quasars (FSRQs) are relatively few despite being the most persistent bright MeV-GeV sources. Focusing on VHE emission, we invest…
Curious Case of CGRaBS J0211+1051: Observational Evidence of Lepto-Hadronic Origin of High-Energy Emission?
Sunil Chandra, Pankaj Kushwaha, Pranjupriya Goswami +1
We present an extensive analysis of the multi-wavelength data of the low-synchrotron-peaked BL Lac object CGRaBS J0211+1051, which has been gathered over more than ten years with m…
Broad-band temporal and spectral study of TeV blazar TXS 0518+211
Avik Kumar Das, Pankaj Kushwaha, Veeresh Singh +3
We present a long-term broad-band temporal and spectral study of a TeV BL Lac source TXS 0518+211 by analyzing nearly 16 years (MJD 54682 -- 60670) of simultaneous optical, UV and…
X-ray variability of VHE detected FSRQs: A comparative study
Lekshmi Dathan, Pankaj Kushwaha
Flat Spectrum Radio Quasars (FSRQs) are weak sources of very high energy (VHE; E>100 GeV) emission, despite exhibiting strong MeV-GeV emissions that dominate their radiative output…
Signature of Seyfert-like component in a blazar 3C 273 and its reflection-based explanation
Haritma Gaur, Main Pal, Muhammad S. Anjum +4
We present the results of blazar 3C 273 obtained from simultaneous observations obtained using XMM-Newton and NuSTAR satellites during the period 2015-2019 in five epochs. When the…
Spectral Energy Distribution Variability of the Blazar OJ 287 during 2009-2021
Wenwen Zuo, Alok C. Gupta, Minfeng Gu +11
Using nearly simultaneous radio, near-infrared, optical, and ultraviolet data collected since 2009, we constructed 106 spectral energy distributions (SEDs) of the blazar OJ 287. Th…
Simultaneous Optical to X-ray Spectra of OJ 287: Insights into X-ray spectral changes and particle spectra
Pankaj Kushwaha
OJ 287 is one of the most dynamic BL Lacertae objects that has exhibited behaviour representative of the entire blazar class and is also one of the best sources with simultaneous m…
X-ray Flux and Spectral Variability of the Blazar OJ 287 with Suzaku
Dongtao Zhou, Zhongli Zhang, Alok C. Gupta +4
We present analyses of Suzaku XIS light curves and spectra of the BL Lac object OJ 287 with observations positioned primarily around proposed recurrent optical outbursts. The first…
The First VHE Activity of OJ 287 and the Extragalactic Background Light
Sameer Yadav, Pankaj Kushwaha
The BL Lacertae (BL Lac) object OJ 287 underwent an intense X-ray activity phase, exhibiting its brightest recorded X-ray flare in 2016-2017, characterized by much softer X-ray spe…
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…
Origin of the broadband emission from the transition blazar B2 1308+326
Ashwani Pandey, Pankaj Kushwaha, Paul J. Wiita +3
Transition blazars exhibit a shift from one subclass to the next during different flux states. It is therefore crucial to study them to understand the underlying physics of blazars…
Quasi-simultaneous Optical Flux and Polarization Variability of the Binary Super Massive Black Hole Blazar OJ 287 from 2015 to 2023: Detection of an Anticorrelation in Flux and Polarization Variability
Alok C. Gupta, Pankaj Kushwaha, Mauri J. Valtonen +25
We study the optical flux and polarization variability of the binary black hole blazar OJ 287 using quasi-simultaneous observations from 2015 to 2023 carried out using telescopes i…
Multi-wavelength temporal variability of the blazar PKS 1510-089
Q. Yuan, Pankaj Kushwaha, Alok C. Gupta +13
We perform correlation and periodicity search analyses on long-term multi-band light curves of the FSRQ 1510-089 observed by the space-based Fermi--Large Area Telescope in gamma-ra…
On the Spectral Changes of OJ 287: The Lowest X-ray state Spectrum -- extended at Optical-UV and Hard at X-rays
Pankaj Kushwaha
Optical-UV synchrotron spectrum has been argued to be the primary driver of the majority of X-ray spectral changes in the BL Lacertae object OJ 287 during its low and intermediate…
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…
The detection of possible transient Quasi-Periodic Oscillations in the -ray light curve of PKS 0244-470 and 4C+38.41
Avik Kumar Das, Raj Prince, Alok C. Gupta +1
The continuous monitoring capability of Fermi-LAT has enabled the exploration of Quasi-Periodic Oscillations (QPOs) in the -ray light curve of blazar that has given a new perspe…
Long Term Multi-band Near Infra-Red Variability of the Blazar OJ 287 during 2007--2021
Alok C. Gupta, Pankaj Kushwaha, L. Carrasco +9
We present the most extensive and well-sampled long-term multi-band near-infrared (NIR) temporal and spectral variability study of OJ 287, considered to be the best candidate binar…
Spectral States of OJ 287 blazar from Multi-wavelength Observations with
K. P. Singh, P. Kushwaha, A. Sinha +3
We present {\it AstroSat} soft X-ray, near-UV (NUV), and far-UV (FUV) observations of a blazar, OJ~287, carried out in 2017, 2018, and 2020. The simultaneous observations with NuST…
The BL Lac Object OJ 287: Exploring a Complete Spectrum of Issues Concerning Relativistic Jets and Accretion
Pankaj Kushwaha
The BL Lacertae (BL Lac) object OJ 287 is one of the most dynamic blazars across the directly accessible observational windows: spectral, timing, polarization, and imaging. Apart f…
Complex optical/UV and X-ray variability in Seyfert 1 galaxy Mrk 509
Neeraj Kumari, Main Pal, Sachindra Naik +3
We performed a detailed spectral and timing analysis of a Seyfert 1 galaxy Mrk 509 using data from the Neil Gehrels Swift observatory that spanned over ~13 years between 2006 and 2…
Spectro-Timing Analysis of a highly variable narrow-line Seyfert 1 galaxy NGC 4748 with AstroSat and XMM-Newton
Main Pal, Neeraj Kumari, Pankaj Kushwaha +8
We present a detailed timing and spectral study of an extremely variable narrow-line Seyfert~1 galaxy NGC 4748 using observations in the year 2017 and 2014 performed with AstroSat…