With recent advances in CCD technology, it has become possible to detect low-amplitude variability in stars. Thus, the number of low-amplitude variables has increased at an exceptional rate over the past decade. Many of these low-amplitude variables are pulsating stars such as Delta Scuti or Gamma Doradus stars, whose periods are on the orders of hours and days, respectively. One particular place where these variables are being found is in close binary systems. A close binary system has two components separated on the order of tens of solar radii and whose periods are on the order of days. Eclipsing binary systems occur when the orbital plane of the system is aligned such that the stars eclipse each other with respect to Earth’s line of sight. Soydugan et al. (2006) presented a paper in which a small number of eclipsing systems with a Delta Scuti-type pulsating component were analyzed. The group derived an observational relationship between the pulsation and orbital periods, thus indicating a physical phenomenon. The proposed project herein will seek to further determine whether there is a statistically significant relationship between the pulsation period and orbital parameters of close binary systems with a Delta Scuti-type pulsating component by searching for such pulsations in close binary systems using the method of high-precision CCD photometry. / Stellar dynamics -- Observations -- [Delta] Scuti stars in close binary systems. / Department of Physics and Astronomy

Analyses of the light variation of the 6 Scuti star CC Andromedae and of the radial velocity variation of the ß Canis Majoris star 6 Scorpii, a single -line spectroscopic binary, indicate that the long period modulations exhibited are caused by tidal deformations induced in the hydrogen and /or helium ionization zones of each primary by a faint companion, resulting in surface zonal variations of the amplitude and phase of each primary's normal radial pulsations. The variations in the tide raising potential calculated at the center of the apparent disk of o Scorpii correlate very strongly with the observed variations in the phase zero -point of the fundamental pulsation. It is suggested that all the ß Canis Majoris and 6 Scuti stars exhibiting long period modulation, and probably also the RR Lyrae stars showing a Blazhko effect, do so because of tidal perturbations induced by faint companions.

In this work, the effect of rotation on the oscillation frequencies of some radially and nonradially oscillating Delta-Scuti stars have been explored. Rotation has been considered as a perturbation and treated up to the second order. Series of evolutionary models have been calculated for the oscillating stars in question and compared with the observational parameters. Three stars are considered: V350 Peg with no rotation, CC And with a rotational velocity Vsini=20 km/s, and BS Tuc with Vsini=130 km/s. We find that splitting in the oscillation frequencies are conspicuous especially in fast rotating stars, with a considerable contribution from the related terms due to second order effect.