Diffuse X-rays from the galactic disk

An anisotropic feature of the diffuse hard X-ray background that tracks the concentration of interstellar hydrogen in the plane of the galaxy is reported. This feature supports a model of galactic X-ray emission by subrelativistic cosmic rays via a bremsstrahlung process. The measurement was carried out on August 9, 1971, using two multianode multilayer gas proportional counters onboard Aerobee 170 flight 13.08. A schematic diagram of the detectors is shown. This type of construction and the appropriate utilization of the signals from the many anodes result in a low detector background, a perequisite before undertaking a measurement of possible small variations in the brightness of the X-ray sky.