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The Fermi-LAT DR1 and DR2 4FGL catalogues feature more than 5000 gamma-ray sources of which about one fourth are not associated with already known objects, and approximately one third are associated with blazars of uncertain nature. We…

High Energy Astrophysical Phenomena · Physics 2021-06-30 S. Germani , G. Tosti , . Lubrano , S. Cutini , I. Mereu , A. Berretta

Since 2008 August the Fermi Large Area Telescope (LAT) has provided continuous coverage of the gamma-ray sky yielding more than 5000 gamma-ray sources, but 54% of the detected sources remain with no certain or unknown association with a low…

High Energy Astrophysical Phenomena · Physics 2020-12-01 Chiaro G. , Kovacevic M. , La Mura G

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

In the recently published 3FGL catalogue, the Fermi/LAT collaboration reports the detection of $\gamma$-ray emission from 3034 sources obtained after four years of observations. The nature of 1010 of those sources is unknown, whereas 2023…

High Energy Astrophysical Phenomena · Physics 2017-06-21 J. Lefaucheur , S. Pita

We conduct X-ray spectral fits on 184 likely counterparts to Fermi-LAT 3FGL unassociated sources. Characterization and classification of these sources allows for more complete population studies of the high-energy sky. Most of these X-ray…

High Energy Astrophysical Phenomena · Physics 2021-03-02 Stephen Kerby , Amanpreet Kaur , Abraham D. Falcone , Michael C. Stroh , Elizabeth C. Ferrara , Jamie A. Kennea , Joseph Colosimo

The Fermi-LAT unassociated sources represent some of the most enigmatic gamma-ray sources in the sky. Observations with the Swift-XRT and -UVOT telescopes have identified hundreds of likely X-ray and UV/optical counterparts in the…

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 latest $\textit{Fermi}$-LAT gamma-ray catalog, 4FGL-DR3, presents a large fraction of sources without clear association to known counterparts, i.e., unidentified sources (unIDs). In this paper, we aim to classify them using machine…

High Energy Astrophysical Phenomena · Physics 2023-04-03 Javier Coronado-Blázquez

We apply a number of statistical and machine learning techniques to classify and rank gamma-ray sources from the Third Fermi Large Area Telescope (LAT) Source Catalog (3FGL), according to their likelihood of falling into the two major…

High Energy Astrophysical Phenomena · Physics 2016-03-23 P. M. Saz Parkinson , H. Xu , P. L. H. Yu , D. Salvetti , M. Marelli , A. D. Falcone

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

We aim to test if a blazar candidate of uncertain-type (BCU) in the third Fermi active galactic nuclei catalog (3LAC) can be potentially classified as a BL Lac object or a flat spectrum radio quasar (FSRQ) by performing a statistical…

High Energy Astrophysical Phenomena · Physics 2017-03-29 Ting-Feng Yi , Jin Zhang , Rui-Jing Lu , Rui Huang , En-Wei Liang

An equivalent width (EW) based classification may cause the erroneous judgement to the flat spectrum radio quasars (FSRQs) and BL Lacerate objects (BL Lac) due to the diluting the line features by dramatic variations in the jet continuum…

High Energy Astrophysical Phenomena · Physics 2023-08-14 Shi-Ju Kang , Yong-Gang Zheng , Qingwen Wu

Despite the fact that blazars constitute the rarest class among active galactic nuclei (AGNs) they are the largest known population of associated $\gamma$-ray sources. Many of the $\gamma$-ray objects listed in the Fermi-Large Area…

We discuss a new method for unveiling the possible blazar AGN nature among the numerous population of Unassociated Gamma-ray sources (UGS) in the Fermi catalogues. Our tool relies on positional correspondence of the Fermi object with X-ray…

High Energy Astrophysical Phenomena · Physics 2017-05-31 Simona Paiano , Alberto Franceschini , Antonio Stamerra

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

Context. Blazars are a distinct subclass of active galactic nuclei (AGN), known for their fast variability, high polarization, and intense emission across the electromagnetic spectrum, from radio waves to gamma rays. Gamma-ray blazar…

High Energy Astrophysical Phenomena · Physics 2025-01-08 N. Álvarez Crespo , A. Domínguez , V. S. Paliya , M. Chamorro Cazorla , P. Sánchez Blázquez , A. Gil de Paz

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

In the third catalog of active galactic nuclei detected by the $Fermi$ Large Area Telescope Clean (3LAC) sample, there are 402 blazars candidates of uncertain type (BCU). The proposed analysis will help to evaluate the potential optical…

High Energy Astrophysical Phenomena · Physics 2020-03-16 Shi-Ju Kang , Kerui Zhu , Jianchao Feng , Qingwen Wu , Bin-Bin Zhang , Yue Yin , Fei-Fei Wang , Yu Liu , Tian-Yuan Zheng

In the forthcoming era of big astronomical data, it is a burden to find out target sources from ground-based and space-based telescopes. Although Machine Learning (ML) methods have been extensively utilized to address this issue, the…

High Energy Astrophysical Phenomena · Physics 2024-01-08 Haitao Cao , Hubing Xiao , Zhijian Luo , Xiangtao Zeng , Junhui Fan

The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic (TS) greater than 25,…

High Energy Astrophysical Phenomena · Physics 2015-09-16 M. Ackermann , M. Ajello , W. Atwood , L. Baldini , J. Ballet , G. Barbiellini , D. Bastieri , J. Gonzalez , R. Bellazzini , E. Bissaldi , R. Blandford , E. Bloom , R. Bonino , E. Bottacini , T. Brandt , J. Bregeon , R. Britto , P. Bruel , R. Buehler , S. Buson , G. Caliandro , R. Cameron , M. Caragiulo , P. Caraveo , J. Casandjian , E. Cavazzuti , C. Cecchi , E. Charles , A. Chekhtman , C. Cheung , J. Chiang , G. Chiaro , S. Ciprini , R. Claus , J. Cohen-Tanugi , L. Cominsky , J. Conrad , S. Cutini , R. D'Abrusco , F. D'Ammando , A. Angelis , R. Desiante , S. Digel , L. Venere , P. Drell , C. Favuzzi , S. Fegan , E. Ferrara , J. Finke , W. Focke , A. Franckowiak , L. Fuhrmann , A. Furniss , P. Fusco , F. Gargano , D. Gasparrini , N. Giglietto , P. Giommi , F. Giordano , M. Giroletti , T. Glanzman , G. Godfrey , I. Grenier , J. Grove , S. Guiriec , J. W. Hewitt , A. Hill , D. Horan , G. J'ohannesson , A. Johnson , W. Johnson , J. Kataoka , M. Kuss , G. Mura , S. Larsson , L. Latronico , C. Leto , J. Li , L. Li , F. Longo , F. Loparco , B. Lott , M. Lovellette , P. Lubrano , G. Madejski , M. Mayer , M. Mazziotta , J. McEnery , P. Michelson , T. Mizuno , A. Moiseev , M. Monzani , A. Morselli , I. Moskalenko , S. Murgia , E. Nuss , M. Ohno , T. Ohsugi , R. Ojha , N. Omodei , M. Orienti , E. Orlando , A. Paggi , D. Paneque , J. Perkins , M. Pesce-Rollins , F. Piron , G. Pivato , T. Porter , S. Rain`o , R. Rando , M. Razzano , S. Razzaque , A. Reimer , O. Reimer , R. Romani , D. Salvetti , M. Schaal , F. Schinzel , A. Schulz , C. Sgr`o , E. Siskind , K. Sokolovsky , F. Spada , G. Spandre , P. Spinelli , L. Stawarz , D. Suson , H. Takahashi , T. Takahashi , Y. Tanaka , J. Thayer , J. Thayer , L. Tibaldo , D. Torres , E. Torresi , G. Tosti , E. Troja , Y. Uchiyama , G. Vianello , B. Winer , K. Wood , S. Zimmer