HEAO-1: low energy X-ray observations of clusters of galaxies.

Results are reported for HEAO 1 low-energy X-ray observations of the Perseus and Virgo clusters of galaxies. The best-fit spectrum for the Perseus cluster indicates thermal bremsstrahlung from a plasma at a temperature of 20 + or - 10 million K, with an absorbing hydrogen column of 2 + or - 1 x 10 to the 21st per sq cm. The best-fit thermal-bremsstrahlung model for the Virgo cluster is obtained for a line centered at 1.15 keV, which is the expected position of the iron line complex at a temperature of 40 million K. An iron abundance of 3.1 (+7, -2.3) x 10 to the -5th relative to hydrogen is determined. This abundance is shown to be within a factor of about 3 of the 'cosmic' value.