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In the course of its operation, the EGRET experiment detected high-energy gamma ray sources at energies above 100 MeV over the whole sky. In this communication, we search for large-scale anisotropy patterns among the catalogued EGRET…

Astrophysics · Physics 2007-05-23 Luis Anchordoqui , Thomas McCauley , Thomas Paul , Olaf Reimer , Diego F. Torres

The large majority of EGRET point sources remain to this day without an identified low-energy counterpart. Whatever the nature of the EGRET unidentified sources, faint unresolved objects of the same class must have a contribution to the…

Astrophysics · Physics 2008-11-26 V. Pavlidou , J. M. Siegal-Gaskins , C. Brown , B. D. Fields , A. V. Olinto

Identifying gamma-ray sources in the Galaxy is hampered by their poor localization, source confusion, and the large variety of potential emitters. Neutron stars and their environment offer various ways to power gamma-ray sources: pulsed…

Astrophysics · Physics 2017-08-23 I. A. Grenier

Since their discovery at radio wavelengths pulsars have been persistent targets for widespread multi-wave observations throughout optics, radio, X-rays, and high-energy gamma-rays. Observations with the EGRET gamma-ray telescope, on board…

Astrophysics · Physics 2007-05-23 A. Konopelko

The ~70 unidentified sources of the EGRET sky survey may be one of its most important legacies. The identification of these sources at other wavelengths is critical to understanding their nature. Many have flat spectra out to 10 GeV which,…

At the end of the EGRET mission, only 6-8 Galactic sources had been identified as young pulsars. Since then, several energetic pulsars have been discovered in EGRET error boxes along the Galactic plane, as well as several pulsar wind…

Astrophysics · Physics 2009-11-10 Mallory S. E. Roberts

The nature of the unidentified gamma-ray point sources in the galactic plane is a long standing puzzle of gamma-ray astronomy. Kaaret and Cottam (1996) showed that 16 of the 25 unidentified gamma-ray point sources near the galactic plane…

Astrophysics · Physics 2007-05-23 Philip Kaaret

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

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

We discuss the nature of the unidentified EGRET source 3EG J1621+8203. In an effort to identify the gamma-ray source, we have examined X-ray images of the field from ROSAT PSPC, ROSAT HRI, and ASCA GIS. Of the several faint X-ray point…

Astrophysics · Physics 2009-11-07 R. Mukherjee , J. Halpern , N. Mirabal , E. V. Gotthelf

A subset of the unidentified EGRET gamma-ray sources with no active galactic nucleus or other conspicuous counterpart appears to be concentrated at medium latitudes. Their long-term variability and their spatial distribution indicate that…

Astrophysics · Physics 2009-11-10 I. A. Grenier , M. M. Kaufman Bernado , G. E. Romero

The limited angular resolution of gamma-ray telescopes prevents the straight identification of the majority of the sources detected so far. While the only certified galactic gamma-ray emitters are associated with pulsars, more than 90% of…

Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope. One of the main goals of this programme is to study the relation between the radio and…

High Energy Astrophysical Phenomena · Physics 2015-06-23 W. Max-Moerbeck , J. L. Richards , T. Hovatta , V. Pavlidou , T. J. Pearson , A. C. S. Readhead , O. G. King , R. Reeves

Using three epochs of VLA observations of the Galactic Plane in the first quadrant taken ~15 years apart, we have conducted a search for a population of variable Galactic radio emitters in the flux density range 1-100 mJy at 6 cm. We find…

Astrophysics of Galaxies · Physics 2015-05-18 Robert H. Becker , David J. Helfand , Richard L. White , Deanne D. Proctor

Most counterparts of the identified low-latitude gamma-ray sources are Isolated Neutron Stars (INSs). They are characterized by an extremely high value of the X/optical flux ratio, therefore a systematic X-ray/optical coverage of the fields…

This Chapter provides a review of $\gamma$-ray sources lying at high Galactic latitudes. Their statistical properties and variability status, as well as studies involving cross correlations with lower frequency catalogs and multiwavelength…

Astrophysics · Physics 2007-05-23 Diego F. Torres

The all-sky survey in high-energy gamma rays (E$>$30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray…

Astrophysics · Physics 2011-05-05 P. Sreekumar

We report on a search for steep spectrum radio sources within the 95% confidence error ellipses of the Fermi unassociated sources from the Large Array Telescope (LAT). Using existing catalogs and the newly released GMRT all-sky survey at…

High Energy Astrophysical Phenomena · Physics 2016-07-27 D. A. Frail , K. P. Mooley , P. Jagannathan , H. T. Intema

We present a multiwavelength analysis of the high-energy gamma-ray source 3EG J2006-2321. The flux of this source above 100 MeV is shown to be variable on time scales of days and months. Optical observations and careful examination of…

Astrophysics · Physics 2009-11-07 P. M. Wallace , J. P. Halpern , A. M. Magalhaes , D. J. Thompson

In a novel approach in observational high-energy gamma-ray astronomy, observations carried out by imaging atmospheric Cherenkov telescopes provide necessary templates to pinpoint the nature of intriguing, yet unidentified EGRET gamma-ray…

Astrophysics · Physics 2008-11-26 Olaf Reimer , Stefan Funk