The ASCA Catalog of Potential X‐Ray Counterparts of GeV Sources

Abstract

We present a catalog of 2-10 keV ASCA Gas ImagingSpectrometer images of fields containing bright sources of GeV emission.The images cover ~85% of the 95% confidence position contour for28 of the 30 sources with >1 GeV fluxes above 4�10-8 phcm-2 s-1. We find an excess of hard X-ray sources withF2-10keV>~10-12 ergs cm-2 s-1 positionallycoincident with unidentified sources of GeV emission. We comment onradio-loud and radio-quiet pulsar candidates, as well as several SNRs andmassive binaries as possible sources of the GeV emission. We alsofind evidence for a class of variable gamma-ray sources associatedwith extended regions of hard X-ray emission, and propose that forthese sources, a significant percentage of the gamma-ray emission isgenerated in synchrotron nebulae surrounding fast, young pulsars.