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The Large Area Telescope (LAT) on board the \emph{Fermi} Gamma-ray Space Telescope has been continuously providing good quality survey data of the entire sky in the high energy range from 30 MeV to 500 GeV and above since August 2008. A…

High Energy Astrophysical Phenomena · Physics 2025-10-13 A. Pathania , K. K. Singh , S. K. Singh , A. Tolamatti , B. B. Singh , K. K. Yadav

The second Fermi-LAT source catalog (2FGL) is the deepest survey of the gamma-ray sky ever compiled, containing 1873 sources that constitute a very complete sample down to an energy flux of about 10^(-11) erg cm^(-2) s^(-1). While…

High Energy Astrophysical Phenomena · Physics 2013-07-01 M. Doert , M. Errando

An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi-Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of E>50…

High Energy Astrophysical Phenomena · Physics 2023-01-25 LAT collaboration , Marco Ajello , Luca Baldini , Jean Ballet , Denis Bastieri , Josefa Becerra Gonzalez , Ronaldo Bellazzini , Alessandra Berretta , Elisabetta Bissaldi , Raffaella Bonino , Ari Brill , Philippe Bruel , Sara Buson , Regina Caputo , Patrizia Caraveo , Teddy Cheung , Graziano Chiaro , Nicolo Cibrario , Stefano Ciprini , Milena Crnogorcevic , Sara Cutini , Filippo D'Ammando , Salvatore De Gaetano , Niccolo Di Lalla , Leonardo Di Venere , Alberto Dominguez , Vandad Fallah Ramazani , Elizabeth Ferrara , Alessio Fiori , Yasushi Fukazawa , Stefan Funk , Piergiorgio Fusco , Viviana Gammaldi , Fabio Gargano , Simone Garrappa , Dario Gasparrini , Nico Giglietto , Francesco Giordano , Marcello Giroletti , David Green , Isabelle Grenier , Sylvain Guiriec , Deirdre Horan , Xian Hou , Taishu Kayanoki , Michael Kuss , Stefan Larsson , Luca Latronico , Tiffany Lewis , Jian Li , Ioannis Liodakis , Francesco Longo , Francesco Loparco , Benoit Lott , Michael Lovellette , Pasquale Lubrano , Grzegorz Madejski , Simone Maldera , Alberto Manfreda , Guillem Marti-Devesa , Mario Nicola Mazziotta , Isabella Mereu , Peter Michelson , Nestor Mirabal , Warit Mitthumsiri , Tsunefumi Mizuno , Maria Elena Monzani , Aldo Morselli , Igor Moskalenko , Michela Negro , Roopesh Ojha , Monica Orienti , Elena Orlando , Jonathan F. Ormes , Zhiyuan Pei , Harold A. Pena-Herazo , Massimo Persic , Melissa Pesce-Rollins , Vahe Petrosian , Roberta Pillera , Helen Poon , Troy Porter , Giacomo Principe , Silvia Raino , Riccardo Rando , Bindu Rani , Massimiliano Razzano , Soebur Razzaque , Anita Reimer , Olaf Reimer , Jeff Scargle , Lorenzo Scotton , Davide Serini , Carmelo Sgro , Eric J. Siskind , Gloria Spandre , Paolo Spinelli , Dan Suson , Hiro Tajima , Diego F. Torres , Janeth Valverde , Hend Yassin , Gabrijela Zaharijas

The extragalactic $\gamma$-rays sky observed by Fermi-Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi-LAT Point Source Catalog (4FGL), are sources showing a multifrequency behavior similar to that of…

Machine learning (ML) and deep learning (DL) techniques are increasingly used across astrophysics, enabled by the growing availability of data and improved acquisition methods. These approaches now support tasks from redshift estimation to…

High Energy Astrophysical Phenomena · Physics 2025-07-09 E. Oukacha , Y. Becherini

Blazars are a highly-variable, radio-loud subclass of active galactic nuclei (AGN). In order to better understand such objects we must be able to easily identify candidate blazars from the growing population of unidentified sources. Working…

High Energy Astrophysical Phenomena · Physics 2015-06-16 Philip S. Cowperthwaite , F. Massaro , R. D'Abrusco , A. Paggi , G. Tosti , Howard A. Smith

Nearly one-third of the sources in the $Fermi$-LAT catalogs lack a lower energy counterpart, hence being referred as unidentified/unassociated gamma-ray sources (UGSs). In order to firmly classify them, dedicated multifrequency follow-up…

The third catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (3LAC) is presented. It is based on the third catalog (3FGL,\cite{3FGL}) of sources detected with a test statistic greater than 25, using the…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Dario Gasparrini , Benoit Lott , Sara Cutini , Stefano Ciprini , Elisabetta Cavazzuti

The classifications of Fermi-LAT unassociated sources are studied using multiple machine learning (ML) methods. The update data from 4FGL-DR3 are divided into high Galactic latitude (HGL, Galactic latitude $|b|>10^\circ$) and low Galactic…

High Energy Astrophysical Phenomena · Physics 2023-11-08 K. R. Zhu , J. M. Chen , Y. G. Zheng , L. Zhang

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the localization of gamma-ray sources with respect to the…

High Energy Astrophysical Phenomena · Physics 2015-06-04 F. Massaro , R. D'Abrusco , G. Tosti , M. Ajello , A. Paggi. D. Gasparrini

A large fraction of Fermi-Large Area Telescope (LAT) sources in the fourth Fermi-LAT 14 yr catalog (4FGL) still remain unidentified (unIDed). We continued to improve our machine-learning pipeline and used it to classify 1206 X-ray sources…

High Energy Astrophysical Phenomena · Physics 2024-08-20 Hui Yang , Jeremy Hare , Oleg Kargaltsev

We have investigated a number of factors that can have significant impacts on the classification performance of $\gamma$-ray sources detected by Fermi Large Area Telescope (LAT) with machine learning techniques. We show that a framework of…

Instrumentation and Methods for Astrophysics · Physics 2020-01-29 Shengda Luo , Alex P. Leung , C. Y. Hui , K. L. Li

The Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) was released in February 2010 and the Fermi-LAT 2-Year Source Catalog (2FGL) appeared in April 2012, based on data from 24 months of operation. Since their releases, many…

Despite the growing number of gamma-ray sources detected by Fermi-LAT, about one third of the sources in each survey remains of uncertain type. We present a new deep neural network approach for the classification of unidentified or…

High Energy Astrophysical Phenomena · Physics 2021-09-28 Thorben Finke , Michael Krämer , Silvia Manconi

The extragalactic $\gamma$-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei (AGNs). Many of the $\gamma$-ray sources included in Fermi -Large Area Telescope Third Source catalog (3FGL) are classified…

We present the third Fermi Large Area Telescope source catalog (3FGL) of sources in the 100 MeV-300 GeV range. Based on the first four years of science data from the Fermi Gamma-ray Space Telescope mission, it is the deepest yet in this…

High Energy Astrophysical Phenomena · Physics 2015-06-10 LAT Collaboration

Aims. We present a sample of 4388 AGNs with available radio core-dominance parameters defined as the ratio of the core flux densities to extended ones, namely, R = Score/Sext., which includes 630 Fermi-detected AGNs respect to the catalog…

Astrophysics of Galaxies · Physics 2019-05-14 Zhi-Yuan Pei , Jun-Hui Fan , Denis Bastieri , Jiang-He Yang , Hu-Bing Xiao

The Fermi-LAT has detected more than 3000 sources in the GeV $\gamma$-ray regime. The majority are extra-galactic and these sources are dominated by blazars. However, $\sim28$ per cent of the sources in Fermi 3LAC are listed as blazar…

High Energy Astrophysical Phenomena · Physics 2017-02-01 L. Klindt , B. van Soelen , P. J. Meintjes , P. Väisänen

Radio-loud sources with blazar-like properties, but having a jet that does not directly point in the direction of the observer are among the most interesting classes of gamma-ray emitters. These sources are known as Misaligned Active…

Astrophysics of Galaxies · Physics 2020-07-30 G. Chiaro , G. La Mura , A. Dominguez , S. Bisogni

Nearly 50% of all sources detected by the Fermi Large Area Telescope are classified as blazars or blazar candidates, one of the most elusive classes of active galaxies. Additional blazars can also be hidden within the sample of unidentified…

High Energy Astrophysical Phenomena · Physics 2020-07-13 E. J. Marchesini , A. Paggi , F. Massaro , N. Masetti , R. D'Abrusco , I. Andruchow