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We report the detection of two new gamma-ray sources in the Fermi-LAT sky (Pass 8) at energies higher than 20 GeV, and confirmed at lower energies, using a source detection tool based on the Minimum Spanning Tree algorithm. One of these…

High Energy Astrophysical Phenomena · Physics 2017-01-25 R. Campana , A. Maselli , E. Bernieri , E. Massaro

We present total and linearly polarized 3 mm Global mm-VLBI Array images of a sample of blazars and radio galaxies from the VLBA-BU-BLAZAR 7 mm monitoring program designed to probe the innermost regions of active galactic nuclei (AGN) jets…

We present a new method for identifying blazar candidates by examining the locus, i.e. the region occupied by the Fermi gamma-ray blazars in the three-dimensional color space defined by the WISE infrared colors. This method is a refinement…

High Energy Astrophysical Phenomena · Physics 2015-06-15 R. D'Abrusco , F. Massaro , A. Paggi , N. Masetti , G. Tosti , M. Giroletti , H. A. Smith

We employ an efficient method for identifying gamma-ray sources across the entire sky, leveraging advanced algorithms from Fermi p y, and cleverly utilizing the Galactic diffuse background emission model to partition the entire sky into 72…

High Energy Astrophysical Phenomena · Physics 2024-12-30 Y. C. Xiang , P. Feng , X. F. Lan

In the fourth \emph{Fermi} Large Area Telescope source catalog (4FGL), 5064 $\gamma$-ray sources are reported, including 3207 active galactic nuclei (AGNs), 239 pulsars, 1336 unassociated sources, 92 sources with weak association with…

High Energy Astrophysical Phenomena · Physics 2021-02-10 Kerui Zhu , Shi-Ju Kang , Yong-Gang Zheng

Blazars, a subset of powerful active galactic nuclei, feature relativistic jets that shine in a broadband electromagnetic radiation, e. g. from radio to TeV emission. Here I present the results of the studies that explore gamma-ray and…

High Energy Astrophysical Phenomena · Physics 2022-10-18 Gopal Bhatta

The Large Area Telescope on the Fermi gamma-ray Space Telescope provides unprecedented sensitivity for all-sky monitoring of gamma-ray activity. It has detected a few Galactic sources, including 2 gamma-ray binaries and a microquasar. In…

High Energy Astrophysical Phenomena · Physics 2016-11-15 Sylvain Chaty

A list of 205 gamma-ray strong objects was reported recently as a result of a 3-month integration with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. We attempted identification of these objects, cross-correlating…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Y. Y. Kovalev

The Fermi Large Area Telescope (Fermi-LAT) has recently revealed a large population of gamma-ray emitting millisecond pulsars (MSPs) in our Galaxy. We aim to infer the properties of the Galactic population of gamma-ray emitting MSPs from…

Astrophysics of Galaxies · Physics 2015-06-15 Tristan Grégoire , Jürgen Knödlseder

After three years of polarimetric monitoring of blazars, the RoboPol project has uncovered several key characteristics of polarimetric rotations in the optical for these most variable sources. The most important of these is that…

High Energy Astrophysical Phenomena · Physics 2019-04-11 Dmitry Blinov , Vasiliki Pavlidou

We present optical spectroscopy secured at the 10m Gran Telescopio Canarias of the counterparts of 20 extragalactic gamma-ray sources detected by the Fermi satellite. The observations allow us to investigate the nature of these sources and…

Astrophysics of Galaxies · Physics 2017-12-27 Simona Paiano , Renato Falomo , Alberto Franceschini , Aldo Treves , Riccardo Scarpa

The technique of Faraday tomography is a key tool for the study of magnetised plasmas in the new era of broadband radio polarisation observations. In particular, observations at metre-wavelengths provide significantly better Faraday depth…

High Energy Astrophysical Phenomena · Physics 2018-12-03 Shane P. O'Sullivan , M. Brüggen , C. L. Van Eck , M. J. Hardcastle , M. Haverkorn , T. W. Shimwell , C. Tasse , V. Vacca , C. Horellou , G. Heald

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This…

High Energy Astrophysical Phenomena · Physics 2015-05-18 The Fermi LAT , the GBM Collaboration , : , A. A. Abdo

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

In the first 3.5 years of operations the Fermi LAT detected several sources with daily fluxes brighter than F(E>100MeV) > 10^{-6} ph/cm^2/s, the threshold set by the Fermi Collaboration for issuing an Astronomer Telegram. We focus the…

High Energy Astrophysical Phenomena · Physics 2013-03-13 S. Buson , D. Bastieri , F. D'Ammando , G. Tosti

The F-GAMMA-project is the coordinated effort of several observatories to understand the AGN phenomenon and specifically blazars via multi-frequency monitoring in collaboration with the {\sl Fermi}-GST satellite since January 2007. The core…

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

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 present a likelihood profile stacking technique based on the {\it Fermi}-Large Area Telescope (LAT) data to explore the $\gamma$-ray characteristics of {\it Fermi}-LAT undetected astrophysical populations. The pipeline is applied to a…

High Energy Astrophysical Phenomena · Physics 2019-09-10 Vaidehi S. Paliya , Alberto Dominguez , Marco Ajello , Anna Franckowiak , Dieter Hartmann

A significant fraction ($\sim 30$ %) of the gamma-ray sources listed in the second $\textit{Fermi}$ LAT (2FGL) catalog is still of unknown origin, being not yet associated with counterparts at lower energies. Using the available information…