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The nature of most of the ~300 high-energy gamma-ray sources discovered by the EGRET instrument aboard the Gamma-ray Observatory (GRO) between 1991 and 1999 is one of the greatest enigmas in high-energy astrophysics. While about half of the…

High Energy Astrophysical Phenomena · Physics 2009-02-05 R. P. Mignani

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

Excess of gamma rays with a spherical morphology around the Galactic center (GC) observed in the Fermi large area telescope (LAT) data is one of the most intriguing features in the gamma-ray sky. The excess has been interpreted by…

High Energy Astrophysical Phenomena · Physics 2024-06-07 Dmitry V. Malyshev

We report on a search for steep spectrum radio sources within the 95% confidence error ellipses of the Fermi unassociated sources from the Large Array Telescope (LAT). Using existing catalogs and the newly released GMRT all-sky survey at…

High Energy Astrophysical Phenomena · Physics 2016-07-27 D. A. Frail , K. P. Mooley , P. Jagannathan , H. T. Intema

Very high-energy (VHE; E > 100 GeV) gamma-rays have been detected from a wide range of astronomical objects, such as SNRs, pulsars and pulsar wind nebulae, AGN, gamma-ray binaries, molecular clouds, and possibly star-forming regions as…

High Energy Astrophysical Phenomena · Physics 2010-01-19 P. H. Thomas Tam , Stefan Wagner , Omar Tibolla , Ryan Chaves

Astrophysicists are interested in recovering the 3D gas emissivity of a galaxy cluster from a 2D image taken by a telescope. A blurring phenomenon and presence of point sources make this inverse problem even harder to solve. The current…

The minimum variability timescale (MVT) is a key observable used to probe the central engines of Gamma-Ray Bursts (GRBs) by constraining the emission region size and the outflow Lorentz factor. However, its interpretation is often…

High Energy Astrophysical Phenomena · Physics 2026-02-13 S. Bala , P. Veres , A. Goldstein , R. Sonawane , R. Samanta , S. Iyyani

Statistical properties of photon count maps have recently been proven as a new tool to study the composition of the gamma-ray sky with high precision. We employ the 1-point probability distribution function of 6 years of Fermi-LAT data to…

High Energy Astrophysical Phenomena · Physics 2016-08-01 Hannes-S. Zechlin , Alessandro Cuoco , Fiorenza Donato , Nicolao Fornengo , Marco Regis

The spatial extension of a gamma-ray source is an essential ingredient to determine its spectral properties as well as its potential multi-wavelength counterpart. The capability to spatially resolve gamma-ray sources is greatly improved by…

High Energy Astrophysical Phenomena · Physics 2018-04-12 The Fermi LAT Collaboration , M. Ackermann , M. Ajello , L. Baldini , J. Ballet , G. Barbiellini , D. Bastieri , R. Bellazzini , E. Bissaldi , E. D. Bloom , R. Bonino , E. Bottacini , T. J. Brandt , J. Bregeon , P. Bruel , R. Buehler , R. A. Cameron , M. Caragiulo , P. A. Caraveo , D. Castro , E. Cavazzuti , C. Cecchi , E. Charles , A. Chekhtman , C. C. Cheung , G. Chiaro , S. Ciprini , J. M. Cohen , D. Costantin , F. Costanza , S. Cutini , F. D'Ammando , F. de Palma , R. Desiante , S. W. Digel , N. Di Lalla , M. Di Mauro , L. Di Venere , C. Favuzzi , S. J. Fegan , E. C. Ferrara , A. Franckowiak , Y. Fukazawa , S. Funk , P. Fusco , F. Gargano , D. Gasparrini , N. Giglietto , F. Giordano , M. Giroletti , D. Green , I. A. Grenier , M. -H. Grondin , L. Guillemot , S. Guiriec , A. K. Harding , E. Hays , J. W. Hewitt , D. Horan , X. Hou , G. Jóhannesson , T. Kamae , M. Kuss , G. La Mura , S. Larsson , M. Lemoine-Goumard , J. Li , F. Longo , F. Loparco , P. Lubrano , J. D. Magill , S. Maldera , D. Malyshev , A. Manfreda , M. N. Mazziotta , P. F. Michelson , W. Mitthumsiri , T. Mizuno , M. E. Monzani , A. Morselli , I. V. Moskalenko , M. Negro , E. Nuss , T. Ohsugi , N. Omodei , M. Orienti , E. Orlando , J. F. Ormes , V. S. Paliya , D. Paneque , J. S. Perkins , M. Persic , M. Pesce-Rollins , V. Petrosian , F. Piron , T. A. Porter , G. Principe , S. Raino , R. Rando , M. Razzano , S. Razzaque , A. Reimer , O. Reimer , T. Reposeur , C. Sgro , D. Simone , E. J. Siskind , F. Spada , G. Spandre , P. Spinelli , D. J. Suson , D. Tak , J. B. Thayer , D. J. Thompson , D. F. Torres , G. Tosti , E. Troja , G. Vianello , K. S. Wood , M. Wood

A direct search of $\gamma$-ray emission centered on multi-frequency selected candidates is a valuable complementary approach to the standard search adopted in current $\gamma$-ray Fermi-LAT catalogs. Our candidates are part of the 2WHSP…

High Energy Astrophysical Phenomena · Physics 2017-02-15 Bruno Arsioli , Yu-Ling Chang

We present results of variability study of a sample of 20 powerful blazars using Fermi/LAT (0.1--300 GeV) observations. We studied decade-long observations applying various analysis tools such as flux distribution, symmetry analysis, and…

High Energy Astrophysical Phenomena · Physics 2021-07-27 Gopal Bhatta , Niraj Dhital

Relativistic amplification boosts the contribution of the jet base to the total emission in blazars, thus making single dish observations useful and practical to characterise their physical state, particularly during episodes of enhanced…

Instrumentation and Methods for Astrophysics · Physics 2020-01-15 Marcello Giroletti , Simona Righini

Because of the relatively broad angular resolution of current gamma-ray instruments in the MeV-GeV energy range, the photons of a given source are mixed with those coming from nearby sources or diffuse background. This source confusion…

Instrumentation and Methods for Astrophysics · Physics 2019-02-06 P. Bruel

To uniformly determine the properties of supernova remnants (SNRs) at high energies, we have developed the first systematic survey at energies from 1 to 100 GeV using data from the Fermi Large Area Telescope. Based on the spatial overlap of…

High Energy Astrophysical Phenomena · Physics 2016-05-19 Fabio Acero , Markus Ackermann , Marco Ajello , Luca Baldini , Jean Ballet , Guido Barbiellini , Denis Bastieri , Ronaldo Bellazzini , E. Bissaldi , Roger Blandford , E. D. Bloom , Raffaella Bonino , Eugenio Bottacini , J. Bregeon , Philippe Bruel , Rolf Buehler , S. Buson , G. A. Caliandro , Rob A. Cameron , R Caputo , Micaela Caragiulo , Patrizia A. Caraveo , Jean Marc Casandjian , Elisabetta Cavazzuti , Claudia Cecchi , A. Chekhtman , J. Chiang , G. Chiaro , Stefano Ciprini , R. Claus , J. M. Cohen , Johann Cohen-Tanugi , L. R. Cominsky , B. Condon , Jan Conrad , S. Cutini , F. D'Ammando , A. Angelis , F. Palma , Rachele Desiante , S. W. Digel , L. Venere , Persis S Drell , Alex Drlica-Wagner , C. Favuzzi , E. C. Ferrara , Anna Franckowiak , Prof. Yasushi Fukazawa , Prof. Stefan Funk , P. Fusco , Fabio Gargano , Dario Gasparrini , Nicola Giglietto , Paolo Giommi , Francesco Giordano , Marcello Giroletti , Tom Glanzman , Gary Godfrey , G A. Gomez-Vargas , I. A. Grenier , M. -H. Grondin , L. Guillemot , Sylvain Guiriec , M Gustafsson , D. Hadasch , A. K. Harding , M. Hayashida , Elizabeth Hays , J. W. Hewitt , A. B. Hill , Deirdre Horan , X. Hou , Giulia Iafrate , Tobias Jogler , G. J'ohannesson , Anthony S. Johnson , T. Kamae , Hideaki Katagiri , Prof. Jun Kataoka , Junichiro Katsuta , Matthew Kerr , J. Knodlseder , Prof. Dale Kocevski , M. Kuss , Helene Laffon , J. Lande , S. Larsson , Luca Latronico , Marianne Lemoine-Goumard , J. Li , L. Li , Francesco Longo , Francesco Loparco , Michael N. Lovellette , Pasquale Lubrano , J. Magill , S. Maldera , Martino Marelli , Michael Mayer , M. N. Mazziotta , Peter F. Michelson , Warit Mitthumsiri , Tsunefumi Mizuno , Alexander A. Moiseev , Maria Elena Monzani , E. Moretti , Aldo Morselli , Igor V. Moskalenko , Prof. Simona Murgia , Prof. Rodrigo Nemmen , Eric Nuss , Takashi Ohsugi , Nicola Omodei , Monica Orienti , Elena Orlando , Jonathan F. Ormes , David Paneque , J. S. Perkins , Melissa Pesce-Rollins , Prof. Vahe' Petrosian , Frederic Piron , Giovanna Pivato , Troy Porter , S. Rain`o , Riccardo Rando , Massimiliano Razzano , Soebur Razzaque , Anita Reimer , Prof. Olaf Reimer , Matthieu Renaud , Thierry Reposeur , Mr. Romain Rousseau , P. M. Parkinson , J. Schmid , A. Schulz , C. Sgr`o , Eric J Siskind , Francesca Spada , Gloria Spandre , Paolo Spinelli , Andrew W. Strong , Daniel Suson , Hiro Tajima , Hiromitsu Takahashi , T. Tanaka , Jana B. Thayer , D. J. Thompson , L. Tibaldo , Omar Tibolla , Prof. Diego F. Torres , Gino Tosti , Eleonora Troja , Yasunobu Uchiyama , G. Vianello , B. Wells , Kent Wood , M. Wood , Manal Yassine , Stephan Zimmer

We implemented a novel technique to perform the collective spectral analysis of sets of multiple gamma-ray point sources using the data collected by the Large Area Telescope onboard the Fermi satellite. The energy spectra of the sources are…

Instrumentation and Methods for Astrophysics · Physics 2012-08-02 M. N. Mazziotta , F. Loparco , F. de Palma , N. Giglietto

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

This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7 -…

High Energy Astrophysical Phenomena · Physics 2012-08-27 LAT Collaboration , A. A. Abdo

This paper presents a new Bayesian spectral unmixing algorithm to analyse remote scenes sensed via sparse multispectral Lidar measurements. To a first approximation, in the presence of a target, each Lidar waveform consists of a main peak,…

Transient radio signals of astrophysical origin present an avenue for studying the dynamic universe. With the next generation of radio interferometers being planned and built, there is great potential for detecting and studying large…

Instrumentation and Methods for Astrophysics · Physics 2015-05-27 Cathryn M. Trott , Randall B. Wayth , Jean-Pierre R. Macquart , Steven J. Tingay

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