Abstract

The occurrence of short-period variability in a number of bright F-type stars was discovered during an extensive program of UB V photoelectric observations made between October, 1965, and February, 1966. The amplitudes of the new variables are small and change in the manner shown by some of the variables of the a Sct type Observations of the continua of the new variables were made by measuring the intensities at twenty-five discrete between about 3300 and 10000 A using a photoelectric spectrum scanner Coude' spectra at 10 A/mm were used to correct the intensities for line-blanketing effects, and the resulting continua were then compared with the model atmospheres of Mihalas to yield effective temperatures and surface gravities Some of the new variables have higher temperatures and gravities than the previously known variables Higher values of the projected rotational velocity V sin i also occur, and indicate that in this region of the H-R diagram pulsation is not incompatible with rapid rotation More than half the stars appear to be significantly undermassive for normal left-to-right evolution in the H-R diagram, for which masses 1 8 Mo are typical Some of the variables, particularly p Pup and HR 5017, have extremely low values of the pulsation constant Q The stars of lowest mass are consistently cooler than those of higher mass, an effect that is observable in a correlation obtained between log g and log T