THE CHEMICAL-COMPOSITION OF ALGOL SYSTEMS .5. CONFIRMATION OF CARBON DEFICIENCIES IN THE PRIMARIES OF 8 SYSTEMS

We use low-noise CCD spectra of the 4267-angstrom C II line in the spe ctra of eight Algol-type eclipsing binaries to measure the C abundance s of their primaries. A differential LTE analysis of the Algol binarie s with respect to single standard stars of the same spectral type show s marginal to moderate deficiencies of C in the primaries of the binar ies. We find [C/H] abundances of - 0.62 for U CrB, - 0.34 for u Her, l ess-than-or-equal-to + 0.24 for delta Lib, - 0.22 for beta Per, - 0.18 for U Sge, - 0.48 for lambda Tau, - 0.35 for TX UMa and - 0. 16 for R S Vul with respect to the average C abundance of single B-type standar d stars. These results confirm those of Cugier and Hardorp, who have u sed IUE observations of the 1300-angstrom C II lines to determine C ab undances in the same stars. The C deficiencies are a consequence of a previous episode of mass transfer in which the secondary, which was in itially the more massive star, has transferred C-deficient, CNO-cycle processed material to the primary. A comparison of observed and theore tical abundances suggests that the mass transfer cannot have been extr emely non-conservative, although it may have been mildly so.