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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

Recent advances in experimental methods have enabled researchers to collect data on thousands of analytes simultaneously. This has led to correlational studies that associated molecular measurements with diseases such as Alzheimer's, Liver,…

Quantitative Methods · Quantitative Biology 2024-05-20 Divyagna Bavikadi , Ayushi Agarwal , Shashank Ganta , Yunro Chung , Lusheng Song , Ji Qiu , Paulo Shakarian

We present the results of a cluster search in the Fermi-LAT Pass 8 gamma-ray sky by means of the Minimum Spanning Tree algorithm, at energies higher than 10 GeV and at Galactic latitudes higher than 25 degrees. The selected clusters have a…

High Energy Astrophysical Phenomena · Physics 2016-11-07 R. Campana , E. Massaro , E. Bernieri

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 simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate that the…

Associating gamma-ray sources to their low-energy counterparts is one of the major challenges of modern gamma-ray astronomy. In the context of the Fourth Fermi Large Area Telescope Source Catalog (4FGL), the associations rely mainly on…

High Energy Astrophysical Phenomena · Physics 2020-06-03 Raniere de Menezes , Raffaele D'Abrusco , Francesco Massaro , Dario Gasparrini , Rodrigo Nemmen

Classification will be an important first step for upcoming surveys that will detect billions of new sources such as LSST and Euclid, as well as DESI, 4MOST and MOONS. The application of traditional methods of model fitting and…

Astrophysics of Galaxies · Physics 2020-01-29 Crispin Logan , Sotiria Fotopoulou

Recent works have developed samples of blazars from among the Fermi-LAT unassociated sources via machine learning comparisons with known blazar samples. Continued analysis of these new blazars tests the predictions of the blazar sequence…

High Energy Astrophysical Phenomena · Physics 2023-07-17 Stephen Kerby , Abraham D. Falcone

We revisit the blazar sequence exploiting the complete, flux limited sample of blazars with known redshift detected by the Fermi satellite after 4 years of operations (the 3LAC sample). We divide the sources into gamma-ray luminosity bins,…

High Energy Astrophysical Phenomena · Physics 2017-05-31 G. Ghisellini , C. Righi , L. Costamante , F. Tavecchio

The first three months of sky-survey operation with the Fermi Gamma Ray Space Telescope (Fermi) Large Area Telescope (LAT) reveals 132 bright sources at |b|>10 deg with test statistic greater than 100 (corresponding to about 10 sigma). Two…

High Energy Astrophysical Phenomena · Physics 2009-09-30 A. A. Abdo

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

Nowadays, Machine Learning techniques offer fast and efficient solutions for classification problems that would require intensive computational resources via traditional methods. We examine the use of a supervised Random Forest to classify…

Astrophysics of Galaxies · Physics 2022-06-22 I. Marini , S. Borgani , A. Saro , G. Murante , G. L. Granato , C. Ragone-Figueroa , G. Taffoni

We recently started a systematic search of low-energy counterparts of the unidentified gamma-ray sources (UGSs) listed in the Fermi-Large Area Telescope (LAT) First Source Catalog (1FGL) and the Fermi-LAT 2-Year Source Catalog (2FGL).} The…

High Energy Astrophysical Phenomena · Physics 2015-06-24 F. Massaro , M. Landoni , R. D'Abrusco , D. Milisavljevic , A. Paggi , N. Masetti , Howard A. Smith , G. Tosti

Searching for low energy counterparts of gamma-ray sources is one of the major challenges in modern gamma-ray astronomy. In the third Fermi source catalog about 30 % of detected sources are unidentified/unassociated Gamma-ray Sources…

Astrophysics of Galaxies · Physics 2019-03-26 Peña-Herazo , H. A. , Marchesini , E. J. , Álvarez Crespo , N. , Ricci , F. , Massaro , F. , Chavushyan , V. , Landoni , M. , Strader , J. , Chomiuk , L. , Cheung , C. C. , Masetti , N. , Jiménez-Bailón , E. , D'Abrusco , R. , Paggi , A. , Milisavljevic , D. , La Franca , F. , Smith , H. A. , Tosti , G.

Approximately one-third of the gamma-ray sources in the third Fermi-LAT catalog are unidentified or unassociated with objects at other wavelengths. Observations with Swift-XRT have yielded possible counterparts in $\sim$30% of these source…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Amanpreet Kaur , Abraham D Falcone , Michael D Stroh , Jamie A Kennea , Elizabeth C Ferrara

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

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 Catalog of Blazars and other Active Galactic Nuclei detected by the Fermi/LAT (2LAC) includes about 1100 sources, 886 of which comprise the Clean Sample. The general properties of the different populations of sources classified…

High Energy Astrophysical Phenomena · Physics 2012-05-15 B. Lott , E. Cavazzuti , S. Cutini , D. Gasparrini , C. D. Dermer

We report the results of our exploratory program carried out with the Southern Astrophysical Research (SOAR) telescope aimed at associating counterparts and establishing the nature of the Fermi Unidentified gamma-ray Sources (UGS). We…

High Energy Astrophysical Phenomena · Physics 2015-06-24 M. Landoni , F. Massaro , A. Paggi , R. D'Abrusco , D. Milisavljevic , N. Masetti , Howard. A. Smith , G. Tosti , L. Chomiuk , J. Strader , C. C. Cheung

Context. Based on their overwhelming dominance among associated Fermi gamma ray catalogue sources, it is expected that a large fraction of the unidentified Fermi objects are blazars. Through crossmatching between the positions of…