AAS 195th Meeting, January 2000
Session 26. Compact Objects: Old, New and Anomalous Friends
Oral, Wednesday, January 12, 2000, 10:00-11:30am, Hanover F and G

## [26.02] Investigations of GeV Sources in the Galactic Plane

M. S. E. Roberts, R. W. Romani (Stanford University), N. Kawai (RIKEN)

The EGRET instrument on board CGRO has detected ~30 sources brighter than ~4\times10-8 {\rm photons} {\rm cm}-2{\rm s}-1 above 1 GeV (Lamb and Macomb 1997). These sources consist of 6 pulsars, 5 blazars, and 19 unidentified objects located near the Galactic equator. The observed pulsars have very steady emission and 3 have associated pulsar wind nebulae (PWN). The blazars are variable, as are several of the unidentified sources. Various source classes have been suggested for the unidentified sources, including radio-quiet pulsars, SNR, massive stars with strong winds, and accreting black holes. The proposed particle acceleration mechanisms of these sources generally imply the production of non-thermal X-ray and radio emission. We present results of a recently completed ASCA survey of the bright GeV sources (Roberts, Romani, and Kawai 2000) and of radio studies of the regions. Several \gamma-ray contours are found to contain lower energy sources whose X-ray and radio properties are similar to those of young pulsars. Others have extended non-thermal emission suggestive of a PWN but apparently variable \gamma-ray emission. In a few fields we find no plausible X-ray counterpart. We discuss the implications of these observations for the proposed source classes and comment on expected contributions from the new generation of X-ray observatories and GLAST.

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