Short-Period Variability of b, a, and F Stars. III. a Survey of Delta Scuti Variable Stars

Two hundred and thirteen bright field stars were tested photoelectically for short-period variability. Nineteen variables and one suspected variable were found. Of these, two supergiants show irregular variability, one variable has been insufficiently studied, and the remaining variables are Scuti stars. The amplitude and incidence of variability depend critically on the color. The large proportion of variables with small amplitudes close to the observational limit of detection indicates that most stars inside the instability strip probably pulsate. The variables and nonvariables in the instability strip show similar galactic U, V, W velocities. Narrow-band photometric and spectroscopic data have been collected for most of the thirty-nine Sct variables published so far. Determinations of absolute magnitudes for these stars are discussed, and new absolute magnitudes are calculated. Data on all stars inside the instability strip considered to be either variable or nonvariable have been collected, and a further list of suspected variables is given.