X-ray emission from γ-ray sources in the galactic anticentre region

An X-ray survey of three high-energy γ-ray sources in the galactic anticentre region has been conducted using the large area sky survey (LASS) instrument on HEAO 1. The sensitivity of this survey ≲0.5 Uhuru flux units (UFU) is the highest yet reported. Although we do not confirm the recently published detection1 of an X-ray source associated with γ195 + 5 (CG195+4); we report the detection of two, and possibly three, other X-ray sources found in its vicinity. Other than the supernova remnant, IC443, no other discrete X-ray sources have been detected near CG189+1, but there is evidence for diffuse emission or emission from unresolved sources in its vicinity. Three new X-ray sources have been discovered within a few degrees of CG176−7, but none overlaps the γ-ray error box. These results demonstrate that γ-ray sources like CG195+4 and CG176−7 have emission characteristics significantly different from the Crab pulsar, but may be similar to the Vela pulsar. Alternatively, the lack of a detectable X-ray flux suggests that the γ-ray emission arises from cosmic-ray interactions in dense interstellar clouds. An interesting feature of the new X-ray sources detected in this survey is that four of them may be associated with early-type stars which exhibit emission lines.