The hard X-ray spectrum of X Persei

Results of observations of 3U 0352 + 30, the source associated with the X Persei system, in the energy range 12-180 keV are reported. The measurements were made on 1978 August 22 with the UCSD/MIT High-Energy X-ray and Low-Energy Gamma-ray Experiment on HEAO 1. Data taken simultaneously in the energy range 2-50 keV indicate that, in addition to a 7 keV thermal bremsstrahlung component, there is a second component of higher energy. It is found that this higher energy component fits a power law of photon index 1.3 (+0.4, -0.5) and is pulsed at the 13.95 minute period of the lower energy component.