OMC/INTEGRAL photometric observations of pulsating components in eclipsing binaries and characterization of DY Aqr

We present the search for eclipsing binaries with a pulsating component in the first catalogue of optically variable sources observed by Optical Monitoring Camera (OMC)/INTEGRAL, which contains photometric data for more than 1000 eclipsing binaries. Five objects were found and a detailed analysis of one of them, DY Aqr, has been performed. Photometric and spectroscopic observations of DY Aqr were obtained to analyse the binary system and the pulsational characteristics of the primary component. By applying the binary modelling software PHOEBE to the OMC and ground-based photometric light curves, and to the radial velocity curve obtained using echelle high-resolution spectroscopy, the physical parameters of the system have been determined. Frequency analysis of the residual data has been performed using Fourier techniques to identify pulsational frequencies. We have built a grid of theoretical models to classify spectroscopically the primary component as an A7.5V star (plus or minus one spectral subtype). The best orbital fit was obtained for a semidetached system configuration. According to the binary modelling, the primary component has T-eff = 7625 +/- 125 K and log g = 4.1 +/- 0.1 and the secondary component has T-eff = 3800 +/- 200 K and log g = 3.3 +/- 0.1, although it is too faint to isolate its spectral features. From the analysis of the residuals, we have found a main pulsation frequency at 23.37 d(-1), which is typical of a delta Scuti star. In the O-C diagram, no evidence of orbital period changes over the last 8 yr has been found.