Gamma-ray astronomy

Abstract:

We present results from a deep search for radio emission, from the X-ray pulsar systems GX 1+4, GS 0834-430 & 4U 0115+63 which have variously been suggested to possess radio jets and to be good candidates for propeller ejection mechanisms. None of these sources is detected at their optical positions, to 3σ limits of a few hundred μJy. This places upper limits on their radio luminosities and thus on the internal energy and numbers of any relativistic electrons which are three to four orders of magnitude below those of radio-bright X-ray binaries such as SS 433 & Cyg X-3. Spectral and structural information on the proposed 'radio lobes' of GX 1+4 make their association with the source unlikely. The lack of detected radio emission from any X-ray pulsar system is discussed statistically, and it is found that X-ray pulsations and radio emission from X-ray binaries are strongly anti-correlated.