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A majority of the active galactic nuclei (AGN) in the local Universe are classified as low-luminosity AGN (LLAGN), having bolometric luminosities $\lesssim 10^{42} \ \mathrm{erg \ s^{-1}}$. Although high-energy gamma-ray emission is…

High Energy Astrophysical Phenomena · Physics 2026-04-08 Chris Karwin , Nikita Khatiya , Margot Boughelilba , Xiurui Zhao , Anita Reimer , Marco Ajello

We use nine years of gamma-ray data provided by the Fermi Large Area Telescope (LAT) to systematically study the light curves of more than two thousand active galactic nuclei (AGN) included in recent Fermi-LAT catalogs. Ten different…

High Energy Astrophysical Phenomena · Physics 2020-07-01 P. Peñil , A. Domínguez , S. Buson , M. Ajello , J. Otero-Santos , J. A. Barrio , R. Nemmen , S. Cutini , B. Rani , A. Franckowiak , E. Cavazzuti

We collect data at all frequencies for the new sources classified as unknown active galactic nuclei (AGNs) in the latest Burst Alert Telescope (BAT) all-sky hard X-ray catalog. Focusing on the 36 sources with measured redshift, we compute…

High Energy Astrophysical Phenomena · Physics 2021-04-07 Luca Giuliani , Gabriele Ghisellini , Tullia Sbarrato

Active Galactic Nuclei (AGN) are remarkable astronomical sources emitting over the whole electromagnetic spectrum, with different bands providing unique windows on distinct sub-structures and their related physics. AGN come in a large…

High Energy Astrophysical Phenomena · Physics 2023-02-27 Paolo Padovani

The fourth-DR3 version (4FGL-DR3) of the Fermi/LAT catalogue of $\gamma$-ray sources contains $\sim$ 1000 objects at a galactic latitude |b| > 10$^{\circ}$ which are not identified with an optical counterpart (UGS). We performed a…

High Energy Astrophysical Phenomena · Physics 2024-02-20 Alberto Ulgiati , Simona Paiano , Aldo Treves , Renato Falomo , Boris Sbarufatti , Fabio Pintore , Thomas D. Russell , Giancarlo Cusumano

Active galactic nuclei (AGNs) exhibit variability across the entire electromagnetic spectrum with distinct flaring episodes at different frequencies. The high sensitivity and nearly uniform sky coverage of the Large Area Telescope on board…

High Energy Astrophysical Phenomena · Physics 2022-03-02 Filippo D'Ammando

This article focuses on certain variability and emission characteristics of Active Galactic Nuclei (AGN), especially their radio-loud subset consisting of quasars, BL Lacs and $\gamma$-ray detected narrow-line Seyfert 1 galaxies, all of…

Astrophysics of Galaxies · Physics 2019-06-28 Gopal-Krishna , Silke Britzen , Paul Wiita

An analytic relation between the statistics of photons in pixels and the number counts of multi-photon point sources is used to constrain the distribution of gamma-ray point sources below the Fermi detection limit at energies above 1 GeV…

Cosmology and Nongalactic Astrophysics · Physics 2011-09-06 Dmitry Malyshev , David W. Hogg

We report the results of the optical follow-up of a sample of $\gamma$-ray-emitting active galactic nuclei (AGN). New high-quality optical spectra were obtained using Gran Telescopio Canarias with Optical System for Imaging and low-…

The discovery in 2008 of high-energy gamma-rays from Narrow-Line Seyfert 1 Galaxies (NLS1s) made it clear that there were active galactic nuclei (AGN) other than blazars and radio galaxies that can eject powerful relativistic jets. In…

High Energy Astrophysical Phenomena · Physics 2020-09-01 Luigi Foschini

We report the detection of a gamma-ray spectral line at approximately 1.5 GeV in three active galactic nuclei (AGN) using 17 years of Fermi-LAT observations. The sample includes both blazars (with relativistic jets directed toward Earth)…

High Energy Astrophysical Phenomena · Physics 2026-04-02 Shi-Ju Kang , Yue Yin , Yong-Gang Zheng , Qingwen Wu

The second Fermi-LAT source catalog (2FGL) is the deepest all-sky survey available in the gamma-ray band. It contains 1873 sources, of which 576 remain unassociated. Machine-learning algorithms can be trained on the gamma-ray properties of…

High Energy Astrophysical Phenomena · Physics 2014-01-29 M. Doert , M. Errando

The quest to uncover periodic patterns within the $\gamma$-ray emissions of jetted active galactic nuclei (AGN) has recently emerged as a focal point in astrophysics. One of the primary challenges has been the necessity for prolonged…

High Energy Astrophysical Phenomena · Physics 2025-10-23 P. Peñil , A. Domínguez , S. Buson , M. Ajello , S. Adhikari , A. Rico

We calculate the diffuse $\gamma$-ray emission due to the population of misaligned AGN (MAGN) unresolved by the Large Area Telescope (LAT) on the {\it Fermi} Gamma-ray Space Telescope ({\it Fermi}). A correlation between the $\gamma$-ray…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-21 M. Di Mauro , F. Donato , F. Calore

We perform a multi-band statistical analysis of core-dominated superluminal active galactic nuclei (AGN) detected with Fermi Large Area Telescope (LAT). The detection rate of $\gamma$-ray jets is found to be high for optically bright AGN.…

Cosmology and Nongalactic Astrophysics · Physics 2010-06-14 T. G. Arshakian , J. León-Tavares , J. Torrealba , V. H. Chavushyan

We present a search for high-energy $\gamma$-ray emission from 566 Active Galactic Nuclei at redshift $z > 0.2$, from the 2WHSP catalog of high-synchrotron peaked BL Lac objects with eight years of Fermi-LAT data. We focus on a redshift…

High Energy Astrophysical Phenomena · Physics 2020-08-12 Michael W. Toomey , Foteini Oikonomou , Kohta Murase

The relativistic jets produced by some Active Galactic Nuclei (AGNs) are among the most efficient persistent sources of non-thermal radiation and represent an ideal laboratory for studying high-energy interactions. In particular, when the…

High Energy Astrophysical Phenomena · Physics 2023-04-18 G. La Mura , J. Becerra Gonzalez , G. Chiaro , S. Ciroi , J. Otero-Santos

The detection of very-high-energy (VHE; $>$100 GeV) $\gamma$-ray radiation from misaligned jetted Active Galactic Nuclei (AGN) challenges the emission models that primarily explain VHE emissions from beamed AGN, i.e., blazars. Using over 16…

High Energy Astrophysical Phenomena · Physics 2025-08-25 Gunjan Tomar , Vaidehi S. Paliya , D. J. Saikia , C. S. Stalin

The third Fermi-LAT catalog (3FGL) presented the data of the first four years of observations from the Fermi Gamma-ray Space Telescope mission. There are 3034 sources, 1010 of which still remain unidentified. Identifying and classifying…

As a critical part of the Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) program, in November 2007 the Australia Telescope Compact Array (ATCA) started monitoring the radio spectra of a sample of…

High Energy Astrophysical Phenomena · Physics 2012-05-14 J. Stevens , P. G. Edwards , R. Ojha , M. Kadler , F. Hungwe , M. Dutka , S. Tingay , J. P. Macquart , A. Moin , J. Lovell , J. Blanchard