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We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNRs, young pulsars, HII regions and young open clusters were used in…

Astrophysics · Physics 2009-10-28 I. -A. Yadigaroglu , Roger W. Romani

Although the majority of gamma-ray sources still remain unidentified, we have various kinds of information to characterize the observational properties of unidentified EGRET sources. Despite astronomical properties like locations of…

Astrophysics · Physics 2016-01-27 Olaf Reimer

The large majority of EGRET point sources remain without an identified low-energy counterpart, and a large fraction of these sources are most likely extragalactic. Whatever the nature of the extragalactic EGRET unidentified sources, faint…

Astrophysics · Physics 2010-11-11 V. Pavlidou , J. M. Siegal-Gaskins , B. D. Fields , A. V. Olinto , C. Brown

Published EGRET spectra from blazars extend only to 10 GeV, yet EGRET has detected approximately 2000 gamma-rays above 10 GeV of which about half are at high Galactic latitude. We report a search of these high-energy gamma-rays for…

Astrophysics · Physics 2009-11-06 Brenda L. Dingus , David L. Bertsch

The vast majority of the celestial gamma-ray sources detected so far have not yet been identified with secure counterparts at other wavelenghts. Here we report the preliminary evidence of a probable association between galaxy clusters and…

Astrophysics · Physics 2009-11-07 Sergio Colafrancesco

In a recent paper, Romero et al. (1999) have presented the results of a positional correlation analysis of the low-latitude unidentified gamma-ray sources in the Third EGRET catalog with complete lists of galactic objects like supernova…

Astrophysics · Physics 2007-05-23 Gustavo E. Romero , Diego F. Torres , P. Benaglia , J. A. Combi , B. Punsly

The origin of the extragalactic gamma-ray background (EGRB) is still an open question, even after nearly forty years of its discovery. The emission could originate from either truly diffuse processes or from unresolved point sources.…

High Energy Astrophysical Phenomena · Physics 2009-11-09 D. Bhattacharya , P. Sreekumar , R. Mukherjee

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

One way to understand the nonthermal history of the universe is by establishing the origins of the unresolved and truly diffuse extragalactic gamma rays. Dim blazars and radio/gamma galaxies certainly make an important contribution to the…

Astrophysics · Physics 2009-06-23 Charles D. Dermer

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…

Astrophysics · Physics 2009-03-26 J. M. Siegal-Gaskins , V. Pavlidou , A. V. Olinto , C. Brown , B. D. Fields

The limited angular resolution of gamma-ray telescopes prevents a direct identification of the majority of sources detected so far. This is particularly true for the low latitude, probably galactic, ones only 10 % of which has been…

We describe the properties of the blazars detected by EGRET and summarize the results on the calculations of the evolution and luminosity function of these sources. Of the large number of possible origins of extragalactic diffuse gamma-ray…

Astrophysics · Physics 2009-10-31 R. Mukherjee , J. Chiang

Using survey data, we have re-evaluated the correlation of flat spectrum radio sources with EGRET sources in the Northern sky. A likelihood analysis incorporating the radio and X-ray properties and the Gamma-ray source localization is used…

Astrophysics · Physics 2009-11-07 David Sowards-Emmerd , Roger W. Romani , Peter F. Michelson

Gamma-ray bursts are known to be sources of high-energy gamma rays, and are likely to be sources of high-energy cosmic rays and neutrinos. Following a short review of observations of GRBs at multi-MeV energies and above, the physics of…

Astrophysics · Physics 2007-05-23 Charles D. Dermer

One of the main scientific objectives of the recent Fermi mission is investigating the origin of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the gamma-ray source localization with respect to the…

High Energy Astrophysical Phenomena · Physics 2013-03-15 F. Massaro , R. D'Abrusco , A. Paggi , N. Masetti , M. Giroletti , G. Tosti , Howard A. Smith

The EGRET telescope on the Compton Gamma-Ray Observatory detected over 200 sources and the majority of these are still unidentified. At least three subpopulations of EGRET sources have been associated with the Galaxy: bright sources lying…

Astrophysics · Physics 2009-11-10 A. K. Harding , P. L. Gonthier , I. A. Grenier , C. A. Perrot

Over half of GeV gamma-ray sources observed by the EGRET experiment have not yet been identified as known astronomical objects. There is an isotropic component of such unidentified sources, whose number is about 60 in the whole sky. Here we…

Astrophysics · Physics 2009-10-31 Tomonori Totani , Tetsu Kitayama

The identification of point sources poses a great challenge for the high energy community. We present a new approach to evaluate the likelihood of a set of sources being a Galactic population based on the simple assumption that galaxies…

Astrophysics · Physics 2009-04-15 J. M. Siegal-Gaskins , V. Pavlidou , A. V. Olinto , C. Brown , B. D. Fields

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the localization of gamma-ray sources with respect to the…

High Energy Astrophysical Phenomena · Physics 2015-06-04 F. Massaro , R. D'Abrusco , G. Tosti , M. Ajello , A. Paggi. D. Gasparrini

Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new…

Astrophysics · Physics 2008-11-26 Charles D. Dermer