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We have obtained simultaneous and continuous photo-polarization observations of the blazar BL Lacertae in optical and near-infrared (NIR) bands during a historical outburst from 2020 to 2021. In total, fourteen nights of observations were…

We have studied long-term optical, ultraviolet (UV) and X-ray observations of OJ 287 collected with the UVOT and XRT instruments mounted on board the Swift satellite to quantify spectral and temporal variability patterns observed during…

High Energy Astrophysical Phenomena · Physics 2018-02-07 Hubert Siejkowski , Alicja Wierzcholska

The extreme variability of blazars, in both timescale and amplitude, is generally explained as the effect of a relativistic jet closely aligned to the observer's line-of-sight. Due to causality arguments, variability characteristics…

Context. The international whole earth blazar telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from February 22, 2009 to February 25, 2009. This object was chosen due…

The University of Michigan 26-m paraboloid was dedicated to obtaining linear polarization and total flux density observations of blazars from the mid-1960s until June 2012 providing an unprecedented record tracking centimeter-band…

High Energy Astrophysical Phenomena · Physics 2017-11-17 Margo F. Aller , Hugh D. Aller , Philip A. Hughes

We present the results from a study of the long-term optical spectral variations of BL Lacertae, using the long and well-sampled B and R-band light curves of the Whole Earth Blazar Telescope (WEBT) collaboration, binned on time intervals of…

Astrophysics · Physics 2019-08-19 I. E. Papadakis , M. Villata , C. M. Raiteri

Multiband optical photometry data of blazar S5 0716+714 obtained from 2002 to 2019 reveal stable color index change with flux variability. We analyzed this trend under variability caused by the Doppler factor change in the presence of a…

High Energy Astrophysical Phenomena · Physics 2022-04-05 Mark A. Gorbachev , Marina S. Butuzova , Sergey G. Sergeev , Sergey V. Nazarov , Alexey V. Zhovtan

We developed a method to separate a long-term trend from observed temporal variations of polarization in blazars using a Bayesian approach. The temporal variation of the polarization vector is apparently erratic in most blazars, while…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Makoto Uemura , Koji S. Kawabata , Mahito Sasada , Yuki Ikejiri , Kiyoshi Sakimoto , Ryosuke Itoh , Masayuki Yamanaka , Takashi Ohsugi , Shuji Sato , Masaru Kino

We present the results of an observational photo-polarimetry campaign of the blazar PG 1553+113 at optical wavelengths. The blazar was recently detected at very high energies (> 100 GeV) by the H.E.S.S and MAGIC gamma-ray Cherenkov…

High Energy Astrophysical Phenomena · Physics 2015-05-28 I. Andruchow , J. A. Combi , A. J. Muñoz-Arjonilla , G. E. Romero , S. A. Cellone , J. Martí

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…

Rapid, multi-color optical monitoring carried out for a multiwavelength campaign during 22-27 August 2000 is presented for the bright and variable BL Lac object PKS 2005-489. Previous multiwavelength monitoring campaigns of PKS 2005-489…

Astrophysics · Physics 2008-11-26 T. A. Rector , E. S. Perlman

We present results of a microvariability polarization study in the violently variable quasar 3C279. We have resolved the polarization curves in the V band for this object down to timescales of minutes. We found two main components in the…

Astrophysics · Physics 2009-11-10 I. Andruchow , S. A. Cellone , G. E. Romero , T. P. Dominici , Z. Abraham

This paper presents an investigation of spectral properties of 10 millisecond pulsars (MSPs) discovered by the uGMRT, observed from 2017-2023 using band 3 (300-500 MHz) and 4 (550-750 MHz) of uGMRT. For these MSPs, we have reported a range…

High Energy Astrophysical Phenomena · Physics 2024-08-15 Rahul Sharan , Bhaswati Bhattacharyya , Sangita Kumari , Jayanta Roy , Ankita Ghosh

We present a comprehensive 20-year multiwavelength variability study of the blazar PKS 2155-304, one of the most luminous and extensively monitored high-frequency-peaked BL Lac objects in the southern hemisphere. Using Fermi-LAT…

High Energy Astrophysical Phenomena · Physics 2026-04-02 A. Wierzcholska , M. Zacharias

Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei (AGN) whose optical variability characteristics have not been well investigated. We present here the results of our investigation on the optical flux…

Astrophysics of Galaxies · Physics 2025-05-07 Subhashree Swain , Vaidehi S. Paliya , D. J. Saikia , C. S. Stalin , Arya Venugopal , A. K. Bhavya , C. D. Ravikumar

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. These SEDs were well-fitted by a log-parabolic model. By…

The quasar-type blazar 4C 38.41 (B3 1633+382) experienced a large outburst in 2011, which was detected throughout the entire electromagnetic spectrum. We present the results of low-energy multifrequency monitoring by the GASP project of the…

We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with ~0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous delta I/I > 25% flares over timescales as short as…

High Energy Astrophysical Phenomena · Physics 2014-09-08 R. Edelson , R. Mushotzky , S. Vaughan , J. Scargle , P. Gandhi , M. Malkan , W. Baumgartner

The RoboPol instrument and the relevant program was developed in order to conduct a systematic study of the optical polarisation variability of blazars. Driven by the discovery that long smooth rotations of the optical polarisation plane…

We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We use the second data release of the 144 MHz LOFAR Two-metre Sky Survey to produce circularly-polarised maps with…