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We study a sample of 30 high-redshift blazars ($z>2.5$) by means of spectra and the radiation mechanism with Fermi Large Area Telescope $\gamma$-ray observations spanning 15 years. Three models -- the power law, power law with an…

High Energy Astrophysical Phenomena · Physics 2025-01-27 Fan Wu , Benzhong Dai

A handedness in the arrival directions of high-energy photons from outside our Galaxy can be related to the helicity of an intergalactic magnetic field. Previous estimates by arXiv:1310.4826 and arXiv:1412.3171 showed a hint of a signal…

High Energy Astrophysical Phenomena · Physics 2020-07-31 Julia Asplund , Guðlaugur Jóhannesson , Axel Brandenburg

Blazar flares seen by the Fermi Gamma-Ray Space Telescope Large Area Telescope (Fermi LAT) are often followed up by Target of Opportunity (ToO) requests to the Neil Gehrels Swift Observatory (Swift). Using flares identified in the daily…

High Energy Astrophysical Phenomena · Physics 2019-01-29 Christina D. Moraitis , D. J. Thompson

Gamma ray observations from a few hundred MeV up to tens of TeV are a valuable tool for studying particle acceleration and diffusion within our galaxy. Constructing a coherent physical picture of particle accelerators such as supernova…

Instrumentation and Methods for Astrophysics · Physics 2019-08-16 Alisha Chromey

In three years of observations since the beginning of nominal science operations in August 2008, the Large Area Telescope (LAT) on board the Fermi Gamma Ray Space Telescope has observed high-energy (>20 MeV) \gamma-ray emission from 35…

High Energy Astrophysical Phenomena · Physics 2015-06-15 LAT Collaboration

Gamma-ray bursts (GRBs) are promising cosmological probes for exploring the Universe at intermediate redshifts ($z$). We analyze 151 Fermi-observed long GRBs (datasets A123 and A28) to simultaneously constrain the Amati correlation and…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-02 Shulei Cao , Bharat Ratra

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

We describe an improved method of mapping the gamma-ray sky by applying the Linear Radon Transform to data from BATSE on NASA's CGRO. Based on a method similar to that used in medical imaging, we use the relatively sharp (~0.25 deg) limb of…

High Energy Astrophysical Phenomena · Physics 2009-12-22 G. L. Case , M. L. Cherry , J. C. Ling , M. Lo , T. Shimizu , Wm. A. Wheaton

Consistent experiment data are crucial to adjust parameters of physics models and to determine best estimates of observables. However, often experiment data are not consistent due to unrecognized systematic errors. Standard methods of…

Nuclear Theory · Physics 2018-03-05 Georg Schnabel

The Fermi-LAT collaboration recently confirmed a discrepancy between the observed longitudinal profile of gamma-ray diffuse emission from the Galaxy and that computed with numerical codes assuming that Cosmic Rays (CRs) are produced by…

High Energy Astrophysical Phenomena · Physics 2013-07-01 Daniele Gaggero , Carmelo Evoli , Dario Grasso , Luca Maccione

Prompt gamma-ray burst spectra evolve on short time scales, suggesting that time-resolved spectral fits may help diagnose the still unknown prompt emission mechanism. We use broad-band gamma-ray data from the RHESSI spacecraft to test…

High Energy Astrophysical Phenomena · Physics 2015-05-13 Eric C. Bellm

Single-cell data integration can provide a comprehensive molecular view of cells, and many algorithms have been developed to remove unwanted technical or biological variations and integrate heterogeneous single-cell datasets. Despite their…

Quantitative Methods · Quantitative Biology 2024-03-04 Rong Ma , Eric D. Sun , David Donoho , James Zou

A new technique is presented for producing images from interferometric data. The method, ``smear fitting'', makes the constraints necessary for interferometric imaging double as a model, with uncertainties, of the sky brightness…

Astrophysics · Physics 2009-11-11 Robert I. Reid

The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope detected a gamma-ray source that is spatially consistent with the location of Eta Carinae. This source has been persistently bright since the beginning of the LAT…

High Energy Astrophysical Phenomena · Physics 2012-08-27 The Fermi LAT collaboration

Blazars are a subclass of active galactic nuclei (AGN) having relativistic jets aligned within a few degrees of our line-of-sight and form the majority of the AGN detected in the TeV regime. The Fermi-Large Area Telescope (LAT) is a…

High Energy Astrophysical Phenomena · Physics 2023-07-04 Atreya Acharyya , Alberto C. Sadun

In this paper, we compile a \emph{Fermi} sample of the \emph{long} GRB observations from 15 years of GBM catalogue with identified redshift, in which the GOLD sample contains 123 long GRBs at $z\le5.6$ and the FULL sample contains 151 long…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-04 Huifeng Wang , Nan Liang

We present an incremental version (4FGL-DR2, for Data Release 2) of the fourth Fermi-LAT catalog of gamma-ray sources. Based on the first ten years of science data in the energy range from 50 MeV to 1 TeV, it uses the same analysis methods…

High Energy Astrophysical Phenomena · Physics 2020-12-18 J. Ballet , T. H. Burnett , S. W. Digel , B. Lott

Traditional binned statistics such as $\chi^2$ suffer from information loss and arbitrariness of the binning procedure. We point out that the underlying statistical quantity (the log likelihood $L$) does not require any binning beyond the…

Gamma-ray Bursts (GRB) were discovered by satellite-based detectors as powerful sources of transient $\gamma$-ray emission. The Fermi satellite detected an increasing number of these events with its dedicated Gamma-ray Burst Monitor (GBM),…

Instrumentation and Methods for Astrophysics · Physics 2021-09-29 G. La Mura , U. Barres de Almeida , R. Conceição , A. De Angelis , F. Longo , M. Pimenta , E. Prandini , E. Ruiz-Velasco , B. Tomé

Sensitivity of searches for extended emission around gamma-ray sources is naturally limited by the precision of the knowledge of the Point Spread Function (PSF) of gamma-ray telescopes. Inaccuracies in the PSF models of the Fermi Large Area…

High Energy Astrophysical Phenomena · Physics 2026-02-17 J. Blunier , A. Neronov , D. Semikoz
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