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Related papers: {\it Fermi}-LAT Stacking Analysis Technique: An Ap…

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We compute the sensitivity to dark matter annihilations for the forthcoming large Cherenkov Telescope Array (CTA) in several primary channels and over a range of dark matter masses from 30 GeV up to 80 TeV. For all channels, we include…

High Energy Astrophysical Phenomena · Physics 2015-06-29 Valentin Lefranc , Emmanuel Moulin , Paolo Panci , Joseph Silk

Very-high energy (VHE; $>$100 GeV) $\gamma$-ray emission originates via some of the most extreme particle acceleration processes in the universe. Considering beamed active galactic nuclei, i.e., blazars, only a small fraction, mainly high…

High Energy Astrophysical Phenomena · Physics 2025-12-10 Sushmita Agarwal , Vaidehi S. Paliya

The proper estimation of the background is a crucial component of data analyses in astrophysics, such as source detection, temporal studies, spectroscopy, and localization. For the case of the Large Area Telescope (LAT) on board the Fermi…

Instrumentation and Methods for Astrophysics · Physics 2013-08-28 V. Vasileiou

The TeV extragalactic sky is dominated by blazars, radio-loud active galactic nuclei with a relativistic jet pointing towards the Earth. Blazars show variability that can be quite exceptional both in terms of flux (orders of magnitude of…

High Energy Astrophysical Phenomena · Physics 2023-09-19 M. Cerruti , J. Finke , G. Grolleron , J. P. Lenain , T. Hovatta , M. Joshi , E. Lindfors , P. Morris , M. Petropoulou , P. Romano , S. Vercellone , M. Zacharias

The sensitivity of the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope allows detection of thousands of new gamma-ray sources and detailed characterization of the spectra and variability of bright sources.…

Instrumentation and Methods for Astrophysics · Physics 2015-03-18 Matthew Kerr

The Fermi Gamma-ray Space Telescope is producing the most detailed inventory of the gamma-ray sky to date. Despite tremendous achievements approximately 25% of all Fermi extragalactic sources in the Second Fermi LAT Catalogue (2FGL) are…

High Energy Astrophysical Phenomena · Physics 2012-12-12 T. Hassan , N. Mirabal , J. L. Contreras , I. Oya

Radio galaxies are uncommon $\gamma$-ray emitters, and only low redshift radio galaxies are detected with Fermi-LAT. However, they offer potential insights into the emission mechanisms of active galaxies, particularly as the alignment of…

High Energy Astrophysical Phenomena · Physics 2020-06-17 Max Harvey , Cameron B. Rulten , Paula M. Chadwick

We report a statistically significant detection of cumulative $\gamma$-ray emission from a stacked sample of SPT-SZ selected galaxy clusters using 16.4 years of data from the Fermi Gamma-Ray Space Telescope's Large Area Telescope (LAT). By…

High Energy Astrophysical Phenomena · Physics 2025-06-05 Siddhant Manna , Shantanu Desai

Recently, a new method to constrain the distances of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed. The underlying assumption is that the Very High Energy (VHE, E > 100 GeV) spectrum…

High Energy Astrophysical Phenomena · Physics 2011-11-04 E. Prandini , M. Mariotti , F. Tavecchio

Blazars can be detected from very large distances due to their high luminosity. However, the detection of $\gamma$-ray emission of blazars beyond $z=3$ has only been confirmed for a small number of sources. Such observations probe the…

We report on VERITAS very-high-energy (VHE; E>100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band,…

This is the first of a series of papers aimed at characterizing the populations detected in the high-latitude sky of the {\it Fermi}-LAT survey. In this work we focus on the intrinsic spectral and flux properties of the source sample. We…

Cosmology and Nongalactic Astrophysics · Physics 2010-09-02 LAT Collaboration

High-redshift ($z >3$) $\gamma$-ray blazars are rare, but they are crucial for our understanding of jet evolution, $\gamma$-ray production and propagation, and the growth of supermassive black holes in the early universe. A new analysis of…

High Energy Astrophysical Phenomena · Physics 2024-06-07 Hai Lei , Ying-Kang Zhang , Xiong Jiang , Sebastian Kiehlmann , Anthony C. S. Readhead , Liang Chen , Neng-Hui Liao , Tao An

An excess of $\gamma$-ray emission from the Galactic Center (GC) region with respect to predictions based on a variety of interstellar emission models and $\gamma$-ray source catalogs has been found by many groups using data from the {\it…

High Energy Astrophysical Phenomena · Physics 2017-10-31 LAT Collaboration

Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine…

High Energy Astrophysical Phenomena · Physics 2017-01-04 A. Kaur , A. Rau , M. Ajello , J. Greiner , D. H. Hartmann , V. S. Paliya , A. Dominguez , J. Bolmer , P. Schady

The nature of dark matter is a longstanding enigma of physics; it may consist of particles beyond the Standard Model that are still elusive to experiments. Among indirect search techniques, which look for stable products from the…

We have recently proposed a simplified scenario for blazars in which these sources are classified as flat-spectrum radio quasars or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted…

High Energy Astrophysical Phenomena · Physics 2015-06-23 P. Padovani , P. Giommi

Studying unidentified {\gamma}-ray sources is important as they may hide new discoveries. We conducted a multiwavelength analysis of 13 unidentified Fermi-LAT sources in the 3FGL catalog that have no known counterparts (Unidentified…

High Energy Astrophysical Phenomena · Physics 2021-07-14 Jean Damascène Mbarubucyeye , Felicia Krauß , Pheneas Nkundabakura

Pulsed gamma rays have been detected with the Fermi Large Area Telescope (LAT) from more than 20 millisecond pulsars (MSPs), some of which were discovered in radio observations of bright, unassociated LAT sources. We have fit the radio and…

High Energy Astrophysical Phenomena · Physics 2011-11-04 Tyrel J. Johnson , Alice K. Harding , Christo Venter

Very high energy (VHE, E >100 GeV) gamma-rays are absorbed via interaction with low-energy photons from the extragalactic background light (EBL) if the involved photon energies are above the threshold for electron-positron pair creation.…

Cosmology and Nongalactic Astrophysics · Physics 2019-08-14 Daniel Mazin , Martin Raue , Bagmeet Behera , Susumu Inoue , Yoshiyuki Inoue , Takeshi Nakamori , Tomonori Totani