X-ray emission possibly coincident with the radio tail of PKS 0301-123.

X-ray, radio, and optical observations are reported for a very poor cluster of galaxies containing the radio source PKS 0301 - 123. A long, 100,000 second X-ray observation using the Einstein Observatory's IPC resulted in the serendipitous discovery of a peculiar extended X-ray morphology associated with the poor cluster. The X-ray emission is extended in the same direction and is approximately the same length as the radio-tailed source, PKS 0301 - 123, which was mapped at 6 and 20 cm with the VLA. Optical redshift observations with the KPNO IIDS on the 2.1 m telescope confirm the identification of the X-ray and radio emission with the poor cluster at z = 0.1. It is argued that the X-ray extension is unlikely to be a chance coincidence of a background source projected onto the foreground cluster. Therefore, four possible mechanisms which might physically link the X-ray and radio emission are considered: thermal bremsstrahlung from a cluster with a flattened potential well; inverse Compton scattering of the relativistic electrons in the radio source, X-ray synchrotron radiation; and heating the cluster gas by the turbulent wake of the radio galaxy. The prospects for future observations of such X-ray/radio coincidences are briefly discussed.