Elemental abundance analyses with DAO spectrograms - XXV. The superficially normal B and A stars alpha draconis, tau Herculis, gamma Lyrae, and HR 7926

Elemental abundances analyses of the superfically normal B and A stars alph a Dra (A0 III), tau Her (B5 IV), gamma Lyr (B9 III), and HR 7926 (B8 II-III ) are performed consistent with previous studies of this series using spect rograms obtained with Reticon and CCD detectors. Comparisons of the first t wo analyses with those of the same stars performed earlier in this series w hich used mostly coadded photographic plates show the general consistency o f the derived elemental abundances. A slight increase in the adopted effect ive temperature produces a corresponding increase in the derived abundances . In these stars the He/H ratios are found to be close to solar. Except for Lyr the metals show for the most part marginally subsolar abundance values . But this star has Al, Ca, Sc, and Sr abundances that are substantially un derabundant as well as other underabundant values.