High spectral resolution observations of the coronal X-ray emission from the RS CVn binary Sigma Corona Borealis

The results of high-resolution observations of the RS CVn binary star Rho Cr B are reported. The observations were carried out using the Focal Plane Crystal Spectrometer (FPCS) onboard the Einstein Observatory satellite. A spectral scan in the interval 800-840 eV shows clear evidence of an X-ray emission line at 826 eV identified with 1S(0)-1P(1) transition of Fe XVII. A prominent peak at 1007 eV in the scan band 986-1014 eV was attributed to a blend of lines produced by highly ionized iron. On the basis of the observed fluxes of the lines and the theoretical calculations of Raymond and Smith (1977), best-fit values of corona temperature and volume emission measures of 6.92 (+0.84 or -0.75) x 10 to the 6th K, and 1.74 (+0.55 or -0.69) x 10 to the 35th are derived, respectively. Some implications of the results are briefly discussed.