منابع مشابه
Variability of Egret Gamma-ray Sources
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 detections and upper limits. These functions can be combined in a uniform manner with a simple model of the flux distribution to characterize the flux variation by a ...
متن کاملA Systematic Search for Short-term Variability of EGRET Sources
The 3rd EGRET Catalog of High-energy Gamma-ray Sources contains 170 unidentified sources, and there is great interest in the nature of these sources. One means of determining source class is the study of flux variability on time scales of days; pulsars are believed to be stable on these time scales while blazars are known to be highly variable. In addition, previous work has demonstrated that 3...
متن کاملEGRET Sources
We compute the variation of the beaming fraction with the e ciency of high energy -ray production in the outer gap pulsar model of Romani and Yadigaroglu. This allows us to correct the uxes observed for pulsars in the EGRET band and to derive a simple estimate of the variation of e ciency with age. Integration of this model over the population of young neutron stars gives the expected number of...
متن کاملUnidentified Egret Sources
The Compton Gamma-Ray Observatory was launched in early 1991 and deorbited in June, 2000. Between April 1991 and September 1995, the Energetic Gamma Ray Experiment Telescope (EGRET) detected 416 gamma-ray excesses with a significance of more than 3 σ above the diffuse background emission. After a careful analysis with a maximum-likelihood procedure, only 271 of these sources were included in th...
متن کاملPopulation studies of the unidentified EGRET sources
The third EGRET catalog contains a large number of unidentified sources. This subset of objects is expected to include known gamma-ray emitters of Galactic origin such as pulsars and supernova remnants, in addition to an extragalactic population of blazars. However, current data allows the intriguing possibility that some of these objects may represent a new class of yet undiscovered gamma-ray ...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2003
ISSN: 0004-637X,1538-4357
DOI: 10.1086/378353