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Population Studies of Radio and Gamma-Ray PulsarsRotation-powered pulsars are one of the most promising candidates for at least some of the 40-50 EGRET unidentified gamma-ray sources that lie near the Galactic plane. Since the end of the EGRO mission, the more sensitive Parkes Multibeam radio survey has detected mere than two dozen new radio pulsars in or near unidentified EGRET sources, many of which are young and energetic. These results raise an important question about the nature of radio quiescence in gamma-ray pulsars: is the non-detection of radio emission a matter of beaming or of sensitivity? The answer is very dependent on the geometry of the radio and gamma-ray beams. We present results of a population synthesis of pulsars in the Galaxy, including for the first time the full geometry of the radio and gamma-ray beams. We use a recent empirically derived model of the radio emission and luminosity, and a gamma-ray emission geometry and luminosity derived theoretically from pair cascades in the polar slot gap. The simulation includes characteristics of eight radio surveys of the Princeton catalog plus the Parkes MB survey. Our results indicate that EGRET was capable of detecting several dozen pulsars as point sources, with the ratio of radio-loud to radio-quiet gamma-ray pulsars increasing significantly to about ten to one when the Parkes Survey is included. Polar cap models thus predict that many of the unidentified EGRET sources could be radio-loud gamma- ray pulsars, previously undetected as radio pulsars due to distance, large dispersion and lack of sensitivity. If true, this would make gamma-ray telescopes a potentially more sensitive tool for detecting distant young neutron stars in the Galactic plane.
Document ID
20040081180
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Harding, Alice K
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Gonthier, Peter
(Hope Coll. Holland, MI, United States)
Coltisor, Stefan
(Hope Coll. Holland, MI, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Astrophysics
Meeting Information
Meeting: Workshop on the Multiwavelength Approach to Unidentified Gamma Ray Sources
Location: Hong Kong
Country: China
Start Date: June 1, 2004
End Date: June 4, 2004
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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