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The Fermi Gamma-ray Space Telescope has been detecting a wealth of sources where the multi-wavelength counterpart is either inconclusive or missing altogether. We present a combination of factors that can be used to identify…

High Energy Astrophysical Phenomena · Physics 2015-06-17 F. Acero , D. Donato , R. Ojha , J. Stevens , P. G. Edwards , E. Ferrara , J. Blanchard , J. E. J. Lovell , D. J. Thompson

The Fermi source 4FGL J1848.7-0129 has been historically related to the globular cluster GLIMPSE-C01 since its very first detection. Although this association is widely accepted, as it appears in the most recent Fermi catalog, it deserves…

High Energy Astrophysical Phenomena · Physics 2022-12-07 Pedro L. Luque-Escamilla , Josep Martí , Enrique Mestre , Jorge A. Combi , Juan F. Albacete-Colombo

With assistance of the identified/associated sources in the second Fermi Large Area Telescope (LAT) catalog, we analyze and resolve the spatial distribution and the distributions of the gamma-ray spectral and variability indices of the…

High Energy Astrophysical Phenomena · Physics 2015-06-15 Zhu Mao , Yun-Wei Yu

Nearly one-third of the gamma-ray sources detected by Fermi are still unidentified, despite significant recent progress in this effort. On the other hand, all the gamma-ray extragalactic sources associated in the second Fermi-LAT catalog…

High Energy Astrophysical Phenomena · Physics 2019-08-19 F. Massaro , R. D'Abrusco , A. Paggi , N. Masetti , M. Giroletti , G. Tosti , Howard A. Smith , S. Funk

Active galactic Nuclei (AGNs) with their relativistic jets pointed toward the observer, are a class of luminous gamma-ray sources commonly known as blazars. The study of this source class is essential to unveil the physical processes…

High Energy Astrophysical Phenomena · Physics 2023-01-18 M. Rajagopal , L. Marcotulli , K. Labrie , S. Marchesi , M. Ajello

In the 4FGL-DR4 point-source catalog of the Large Area Telescope (LAT) onboard NASA's Fermi Gamma-ray Observatory (Fermi-LAT), around a third of the sources are still unidentified (unIDs). In this work, we perform a detailed study of one of…

Dark matter annihilation signals coming from Galactic subhaloes may account for a small fraction of unassociated point sources detected in the Second Fermi-LAT catalogue (2FGL). To investigate this possibility, we present Sibyl, a Random…

High Energy Astrophysical Phenomena · Physics 2015-06-05 N. Mirabal , V. Frias-Martinez , T. Hassan , E. Frias-Martinez

About one third of the gamma-ray sources listed in the second Fermi LAT catalog (2FGL) have no firmly established counterpart at lower energies so being classified as unidentified gamma-ray sources (UGSs). Here we propose a new approach to…

High Energy Astrophysical Phenomena · Physics 2015-06-16 F. Massaro , R. D'Abrusco , M. Giroletti , A. Paggi , N. Masetti , G. Tosti , M. Nori , S. Funk

Pulsars are rapidly-rotating, highly-magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently, only seven were observed to pulse in gamma rays and…

Astrophysics of Galaxies · Physics 2010-09-07 LAT Collaboration

Blazars, including BL Lacs and FSRQs, are the most luminous extragalactic {\gamma}-ray sources. They account for about 56% of the sources listed in the recent Fermi-LAT catalog (4FGL-DR4). The optical and UV spectra of BL Lacs are nearly…

Blazars represent the most abundant class of high-energy extragalactic $\gamma$-ray sources. The subset of blazars known as BL Lac objects is on average closer to Earth and characterized by harder spectra at high energy than the whole…

High Energy Astrophysical Phenomena · Physics 2016-05-26 M. Di Mauro , F. Donato , G. Lamanna , D. A. Sanchez , P. D. Serpico

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

An Artificial Neural Network (ANN) has been employed using a supervised back-propagation scheme to classify 2000 bright sources from the Calgary database of IRAS (Infrared Astronomy Satellite) spectra in the wavelength region of 8-23…

Astrophysics · Physics 2009-11-10 Ranjan Gupta , Harinder P. Singh , K. Volk , S. Kwok

Blazars are the most common sources of $\gamma$-ray photons in the extragalactic sky. Their $\gamma$-ray light curves are characterized by bright flaring episodes, similarly to what is observed at longer wavelengths. These gamma-ray bursts…

High Energy Astrophysical Phenomena · Physics 2025-06-04 Matteo Cerruti

Historically, the blazar population has been poorly understood at low frequencies because survey sensitivity and angular resolution limitations have made it difficult to identify megahertz counterparts. We used the LOFAR Two-Metre Sky…

Based on well-grounded Galactic neutron star populations formed from radio pulsar population syntheses of canonical pulsars (CPs) and millisecond pulsars (MSPs), we use the latest Fermi-LAT catalog (4FGL-DR4) to investigate the implications…

High Energy Astrophysical Phenomena · Physics 2025-06-23 Shawaiz Tabassum , Duncan Lorimer

We analyse 77 \textit{Fermi} sources and their potential low-energy counterparts previously proposed in the literature. These sources were classified as active galactic nuclei, mainly blazars, based on optical spectroscopy. The main goals…

High Energy Astrophysical Phenomena · Physics 2025-09-03 Alberto Ulgiati , Paolo Padovani , Paolo Giommi , Simona Paiano , Ciro Pinto

The third Fermi Large Area Telescope (LAT) $\gamma$-ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the $\gamma$-ray emission of those objects is…

High Energy Astrophysical Phenomena · Physics 2017-04-12 F. K. Schinzel , L. Petrov , G. B. Taylor , P. G. Edwards

Over the last decade more than five thousand gamma-ray sources were detected by the Large Area Telescope (LAT) on board Fermi Gamma-ray Space Telescope. Given the positional uncertainty of the telescope, nearly 30% of these sources remain…

Approximately one-third of existing $\gamma$-ray sources identified by the $\textit{Fermi Gamma-Ray Space Telescope}$ are considered to be unassociated, with no known counterpart at other frequencies/wavelengths. These sources have been the…

High Energy Astrophysical Phenomena · Physics 2023-02-01 S. Bruzewski , F. K. Schinzel , G. B. Taylor