A Survey of EGRET Sources for Pulsed Radio Emission

Abstract

We have made deep searches for pulsed radio signals toward gamma-ray sources detected by the EGRET instrument of the Compton Gamma Ray Observatory. Our observations targeted 19 sources in the second EGRET source catalog (2EG), primarily sources along the Galactic plane without identified counterparts. Our observations also covered eight locations listed in earlier catalogs but not in 2EG. Data were collected at 370, 770, and 1390 MHz with the Green Bank 140 foot telescope. Flux density limits were 0.5-1.0 mJy for slow pulsars, with somewhat less sensitivity at short pulse periods. We discovered no new pulsars. We detected two previously known pulsars, PSR B0611+22 and PSR B1758-23, which are apparently not associated with cataloged gamma-ray sources. Our nondetection of radio pulsars associated with the EGRET sources weakly constrains models of the gamma-ray source population. In particular, we rule out a model in which all the Galactic gamma-ray sources are pulsars with a 50% beaming fraction.