199 citations · 904 across the 44 of their papers we have counts for
45 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…
Tracking down the broadband polarimetric properties of PG 1553+113
Riccardo Middei, Svetlana G. Jorstad, Alan P. Marscher +78
We report on a nine-month monitoring campaign of the blazar PG 1553+113, relying on three observations carried out in 2025 with the Imaging X-ray Polarimetry Explorer (IXPE) and su…
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…
Multiwavelength quasi-periodic variability of the blazar Ton 599
Yu. V. Sotnikova, T. V. Mufakharov, A. E. Volvach +34
During the last 40-50 years, the TeV blazar Ton 599 has systematically experienced major outbursts detected in a wide wavelength range from radio to -rays. In this work, we pres…
POLAMI Multi-Wavelength Polarization Study of AGN Jets: A Millimeter-Optical Comparison
C. Casadio, D. Blinov, I. Agudo +20
Millimeter-band polarimetry offers a powerful probe of AGN jets, accessing regions less affected by opacity and Faraday rotation than at longer radio wavelengths. As part of the PO…
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…
Detection of Compton scattering in the jet of 3C 84
Ioannis Liodakis, Sudip Chakraborty, Frédéric Marin +77
3C 84 is the brightest cluster galaxy in the Perseus Cluster. It is among the closest radio-loud active galaxies and among the very few that can be detected from low frequency radi…
IXPE Observations of the Blazar Mrk 501 in 2022: A Multiwavelength View
L. Lisalda, E. Gau, H. Krawczynski +157
The blazar Markarian 501 (Mrk 501) was observed on three occasions over a 4-month period between 2022 March and 2022 July with the Imaging X-ray Polarimetry Explorer (IXPE). In thi…
Determining the origin of the X-ray emission in blazars through multiwavelength polarization
Ioannis Liodakis, Haocheng Zhang, Stella Boula +48
The origin of the high-energy emission in astrophysical jets from black holes is a highly debated issue. This is particularly true for jets from supermassive black holes that are a…
High optical to X-ray polarization ratio reveals Compton scattering in BL Lacertae's jet
Ivan Agudo, Ioannis Liodakis, Jorge Otero-Santos +147
Blazars, supermassive black hole systems (SMBHs) with highly relativistic jets aligned with the line of sight, are the most powerful long-lived emitters of electromagnetic emission…
Multiband Optical Variability of the Blazar 3C 454.3 on Diverse Timescales
Karan Dogra, Alok C. Gupta, C. M. Raiteri +79
Due to its peculiar and highly variable nature, the blazar 3C 454.3 has been extensively monitored by the WEBT team. Here, we present for the first time these long-term optical flu…
Multi-wavelength picture of the misaligned BL Lac object 3C 371
J. Otero-Santos, C. M. Raiteri, A. Tramacere +52
The BL Lac object 3C 371 is one of the targets that are regularly monitored by the Whole Earth Blazar Telescope (WEBT) Collaboration to study blazar variability on both short and l…
A wiggling filamentary jet at the origin of the blazar multi-wavelength behaviour
C. M. Raiteri, M. Villata, M. I. Carnerero +96
Blazars are beamed active galactic nuclei known for their strong multi-wavelength variability on timescales from years down to minutes. We aim to investigate the suitability of the…
A Two-Week Monitoring Campaign on Mrk 421
W. Peter Maksym, Ioannis Liodakis, M. Lynne Saade +153
X-ray polarization is a unique new probe of the particle acceleration in astrophysical jets made possible through the Imaging X-ray Polarimetry Explorer. Here we report on the firs…
The Method of Searching for Rotations of the Polarization Position Angle of Quasars
S. S. Savchenko, D. A. Morozova, S. G. Jorstad +11
Observations of quasars show that the polarization position angle of the emission coming from them varies greatly over time, including periods called rotations during which the ang…
X-ray and multiwavelength polarization of Mrk 501 from 2022 to 2023
Chien-Ting J. Chen, Ioannis Liodakis, Riccardo Middei +143
We present multiwavelength polarization measurements of the luminous blazar Mrk~501 over a 14-month period. The 2--8 keV X-ray polarization was measured with the Imaging X-ray Pola…
Testing particle acceleration in blazar jets with continuous high-cadence optical polarization observations
Ioannis Liodakis, Sebastian Kiehlmann, Alan P. Marscher +44
Variability can be the pathway to understanding the physical processes in astrophysical jets, however, the high-cadence observations required to test particle acceleration models a…
The variability patterns of the TeV blazar PG 1553+113 from a decade of MAGIC and multi-band observations
MAGIC Collaboration, H. Abe, S. Abe +264
PG 1553+113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high-energy (VHE; >100 GeV) gamma-ray emitter. To b…
Optical circular polarization of blazar S4 0954+65 during high linear polarized states
I. Liodakis, E. Shablovinskaya, D. Blinov +17
Optical circular polarization observations can directly test the particle composition in black holes jets. Here we report on the first observations of the BL Lac type object S4 095…
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…
The Repeating Flaring Activity of Blazar AO 0235+164
Juan Escudero Pedrosa, Iván Agudo, Andrea Tramacere +27
Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes pe…
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…
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…
Multi-messenger characterization of Mrk 501 during historically low X-ray and -ray activity
MAGIC collaboration, H. Abe, S. Abe +322
We study the broadband emission of Mrk 501 using multi-wavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi-LA…