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The variability of the high-energy gamma ray sources in the Third EGRET catalog is analyzed by a new method. We re-analyze the EGRET data to calculate a likelihood function for the flux of each source in each observation, both for…

Astrophysics · Physics 2009-11-10 P. L. Nolan , W. F. Tompkins , I. A. Grenier , P. F. Michelson

Fostered by upcoming data from new generation observational campaigns, we are about to enter a new era for the study of how galaxies form and evolve. The unprecedented quantity of data that will be collected, from distances only marginally…

We calculate the spectrum of blast wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find…

Astrophysics · Physics 2011-09-30 P. Meszaros , M. J. Rees , H. Papathanassiou

Energy based models (EBMs) are appealing for their generality and simplicity in data likelihood modeling, but have conventionally been difficult to train due to the unstable and time-consuming implicit MCMC sampling during contrastive…

Machine Learning · Computer Science 2024-07-23 Junn Yong Loo , Michelle Adeline , Arghya Pal , Vishnu Monn Baskaran , Chee-Ming Ting , Raphael C. -W. Phan

AMORPH utilizes a new Bayesian statistical approach to interpreting X-ray diffraction results of samples with both crystalline and amorphous components. AMORPH fits X-ray diffraction patterns with a mixture of narrow and wide components,…

Data Analysis, Statistics and Probability · Physics 2018-08-15 Michael C. Rowe , Brendon J. Brewer

Astrophysical sources outside the Milky Way, such as active galactic nuclei and star-forming galaxies, leave their imprint on the gamma-ray sky as nearly isotropic emission referred to as the Extragalactic Gamma-Ray Background (EGB). While…

High Energy Astrophysical Phenomena · Physics 2017-01-12 Mariangela Lisanti , Siddharth Mishra-Sharma , Lina Necib , Benjamin R. Safdi

Context. A considerable fraction of the gamma-ray sources discovered with the Energetic Gamma-Ray Experiment Telescope (EGRET) remain unidentified. The EGRET sources that have been properly identified are either pulsars or variable sources…

The response of many materials to applied forces and boundary constraints depends upon internal geometric changes at multiple submacroscopic levels. Hierarchical structured deformations provide a mathematical setting for the description of…

Classical Analysis and ODEs · Mathematics 2025-05-15 Ana Cristina Barroso , José Matias , Marco Morandotti , David R. Owen , Elvira Zappale

We provide our estimates of the intensity of the gamma-ray emission with an energy near 0.1 TeV generated in inrergalactic space in the interactions of cosmic rays with background emissions. We assume that the cosmic ray sources are…

High Energy Astrophysical Phenomena · Physics 2017-08-30 A. V. Uryson

Recent observations by ground-based gamma-ray telescopes have led to the publication of catalogs listing sources observed in the TeV and PeV energy ranges. Photons of such high energy are strongly absorbed during propagation over…

High Energy Astrophysical Phenomena · Physics 2025-02-14 Paolo Lipari , Silvia Vernetto

Energy-based models are a simple yet powerful class of probabilistic models, but their widespread adoption has been limited by the computational burden of training them. We propose a novel loss function called Energy Discrepancy (ED) which…

Machine Learning · Statistics 2023-11-28 Tobias Schröder , Zijing Ou , Jen Ning Lim , Yingzhen Li , Sebastian J. Vollmer , Andrew B. Duncan

Mismodeling the uncertain, diffuse emission of Galactic origin can seriously bias the characterization of astrophysical gamma-ray data, particularly in the region of the Inner Milky Way where such emission can make up over 80% of the photon…

High Energy Astrophysical Phenomena · Physics 2020-10-21 Siddharth Mishra-Sharma , Kyle Cranmer

We study fractional variability as a function of energy from black-hole X-ray binaries on timescales from milliseconds to hundreds of seconds. We build a theoretical model of energy-dependent variability in which the X-ray energy spectrum…

Astrophysics · Physics 2009-11-11 Marek Gierlinski , Andrzej A. Zdziarski

A variety of statistical methods for understanding variability in the time domain for low count rate X-ray and gamma-ray sources are explored. Variability can be detected using nonparametric (Anderson-Darling and overdispersion tests) and…

Instrumentation and Methods for Astrophysics · Physics 2023-05-24 Eric D. Feigelson , Vinay L. Kashyap , Aneta Siemiginowska

Atom probe tomography data is composed of a list of coordinates of the reconstructed atoms in the probed volume. The elemental identity of each atom is derived from time-of-flight mass spectrometry, with no local energetic or chemical…

The newly developed X-ray visibility forward fitting technique is applied to Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data of a limb flare to investigate the energy and height dependence on sizes, shapes, and position…

Solar and Stellar Astrophysics · Physics 2015-05-18 E. P. Kontar , I. G. Hannah , N. L. S. Jeffrey , M. Battaglia

Spatial extension is an important characteristic for correctly associating gamma-ray-emitting sources with their counterparts at other wavelengths and for obtaining an unbiased model of their spectra. We present a new method for quantifying…

Graphical models are ubiquitous tools to describe the interdependence between variables measured simultaneously such as large-scale gene or protein expression data. Gaussian graphical models (GGMs) are well-established tools for…

Methodology · Statistics 2020-01-09 Nilabja Guha , Veera Baladandayuthapani , Bani K. Mallick

We perform a blind search for the variability of the gamma-ray sky in the energy range E>1 GeV using 308 weeks of the Fermi-LAT data. We use the technique based on the comparison of the weekly photon counts and exposures in sky pixels by…

High Energy Astrophysical Phenomena · Physics 2015-12-22 M. S. Pshirkov , G. I. Rubtsov

Three different methods of measuring cosmology with gamma-ray bursts (GRBs) have been proposed since a relation between the $\gamma$-ray energy $E_{\gamma} $ of a GRB jet and the peak energy $E_p$ of the $\nu F_{\nu}$ spectrum in the burst…

Astrophysics · Physics 2009-11-10 D. Xu , Z. G. Dai , E. W. Liang