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Blazars display variable emission across the entire electromagnetic spectrum, with timescales that can range from a few minutes to several years. Our recent work has shown that a sample of five blazars exhibit hints of periodicity with a…

High Energy Astrophysical Phenomena · Physics 2023-10-20 P. Peñil , J. R. Westernacher-Schneider , M. Ajello , A. Domínguez , S. Buson , J. Otero-Santos , L. Marcotulli , N. Torres-Albà , J. Zrake

Blazars are known to exhibit variability across a broad range of timescales. This behavior can include periodicity in their $\gamma$-ray emission, whose clear detection remains an ongoing challenge, partly due to the inherent stochasticity…

High Energy Astrophysical Phenomena · Physics 2025-07-08 P. Peñil , M. Ajello , S. Buson , A. Domínguez , J. R. Westernacher-Schneider , A. Rico , S. Adhikari , J. Zrake

The Fermi Large Area Telescope (Fermi LAT) provides long term systematic monitoring observations of the gamma-ray emission from blazars. The variability properties and the correlation with other wavelength bands are important clues for the…

High Energy Astrophysical Phenomena · Physics 2019-08-13 Stefan Larsson

A majority of blazars exhibit variable emission across the entire electromagnetic spectrum, observed over various time scales. In particular, discernible periodic patterns are detected in the $\gamma$-ray light curves of a few blazars, such…

High Energy Astrophysical Phenomena · Physics 2025-06-18 Alba Rico , A. Domínguez , P. Peñil , M. Ajello , S. Buson , S. Adhikari , M. Movahedifar

Decade-long monitoring of blazars at optical and infrared (OIR) wavelengths with the Small and Moderate Aperture Research Telescope System (SMARTS) in Chile and in $\gamma$-rays with the Fermi Large Area Telescope (LAT) has enabled the…

High Energy Astrophysical Phenomena · Physics 2021-07-14 M. Polkas , M. Petropoulou , G. Vasilopoulos , A. Mastichiadis , M. C. Urry , P. Coppi , C. Bailyn

We present results of variability study of a sample of 20 powerful blazars using Fermi/LAT (0.1--300 GeV) observations. We studied decade-long observations applying various analysis tools such as flux distribution, symmetry analysis, and…

High Energy Astrophysical Phenomena · Physics 2021-07-27 Gopal Bhatta , Niraj Dhital

The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT…

We present the results of a long-term periodicity search in a sample of $\gamma$-ray blazars within a multiwavelength context. These blazars have been selected from the Steward Observatory sample as part of its optical monitoring program…

High Energy Astrophysical Phenomena · Physics 2022-11-16 J. Otero-Santos , P. Peñil , J. A. Acosta-Pulido , J. Becerra González , C. M. Raiteri , M. I. Carnerero , M. Villata

We present an in-depth and systematic variability study of a sample of 20 powerful blazars, including 12 BL Lacs and 8 flat spectrum radio quasars, applying various analysis tools such as flux distribution, symmetry analysis, and time…

High Energy Astrophysical Phenomena · Physics 2020-03-18 Gopal Bhatta , Niraj Dhital

We present a study of the multiwavelength (MW) variability of the blazar AO 0235+164 based on the radio-to-$\gamma$-ray data covering a long time period from 1997 to 2023. The radio data are represented by the 1-22 GHz measurements from the…

The gamma-ray emission of blazar jets shows a pronounced variability and this feature provides limits to the size and to the speed of the emitting region. We study the gamma-ray variability of bright blazars using data from the first 18…

High Energy Astrophysical Phenomena · Physics 2015-05-28 T. Sbarrato , L. Foschini , G. Ghisellini , F. Tavecchio

Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and…

High Energy Astrophysical Phenomena · Physics 2022-10-18 Gopal Bhatta

We carried out a multiwavelength cross-correlation analysis of a sample of 16 blazars detected by Fermi/LAT. The purpose is to investigate if there exists correlations between the distinct bands we analyze in this work. We searched for…

High Energy Astrophysical Phenomena · Physics 2013-04-19 V. Patiño-Álvarez , A. Carramiñana , L. Carrasco , V. Chavushyan

A systematic search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky is performed. Looking for cyclical emission, the sky is binned into equal-area pixels and the generalised…

High Energy Astrophysical Phenomena · Physics 2017-07-20 D. A. Prokhorov , A. Moraghan

Blazars represent dominant population of the extragalactic $\gamma$-ray sources in the Universe. These sources exhibit some characteristic properties like strong and non-thermal continuum emission over the entire electromagnetic spectrum…

High Energy Astrophysical Phenomena · Physics 2020-10-07 K. K. Singh , P. J. Meintjes

In an attempt to constrain and understand the emission mechanism of gamma rays, we perform a cross-correlation analysis of 15 blazars using light curves in millimetre, optical and gamma rays. We use discrete correlation function and…

High Energy Astrophysical Phenomena · Physics 2015-12-15 V. Ramakrishnan , T. Hovatta , M. Tornikoski , K. Nilsson , E. Lindfors , M. Baloković , A. Lähteenmäki , R. Reinthal , L. Takalo

The detection of periodicities in light curves of active galacticnuclei (AGN) could have profound consequences for our understanding of the nature and radiation physics of these objects. At high energies (HE; E>100 MeV) 5 blazars (PG…

High Energy Astrophysical Phenomena · Physics 2020-02-26 F. Ait Benkhali , W. Hofmann , F. M. Rieger , N. Chakraborty

Violent multi-wavelength variabilities are observed in gamma-ray-selected blazars. We present an analysis of long-term light curves for eight bright blazars to explore the co-variation pattern in the gamma-ray and radio bands. We extract…

High Energy Astrophysical Phenomena · Physics 2020-05-27 Hai-Ming Zhang , Zhen-Jie Wang , Jin Zhang , Ting-Feng Yi , Liang Chen , Rui-Jing Lu , En-Wei Liang

Variable \gama-ray emission from blazars, one of the most powerful classes of astronomical sources featuring relativistic jets, is a widely discussed topic. In this work, we present the results of a variability study of a sample of 20…

High Energy Astrophysical Phenomena · Physics 2021-09-22 Jaroslaw Duda , Gopal Bhatta

To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency monitoring in the radio regime. We quantify the radio…

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