Extended Observations of > 7-keV X-Rays from Centaurus X-3 by the OSO-7 Satellite

The UCSD X-ray telescope on board OS 0-7 provided 43 days of continuous coverage of the variable X-ray source Cen X-3 at energies above 7 keV during 1971 December and 1972 January. We detected the 4.8-s pulsation period, the 2.087-day eclipse cycle, and an apparently nonperiodic, low-intensity state lasting more than 12 days. Spectra obtained over the 7-30 keV range during noneclipsed high-intensity states are steeper than those previously reported; typically the flux is E- or E-1 exp (-E/7 keV) photons (cm2 s keV) 1 Large changes, which may be characterized by a number spectral index a varying between 3.0 + 0.2 and 2.0 + 0.3, or by exponential spectra with kT varying from 6 1 2 to 13 1 3 keV, occur at different high-intensity states. Subject headings: eclipsing binaries - spectra, X-ray - X-ray sources