CCD Photometry of Variable Stars

Using the recently refurbished 1.3 m Robotically Controlled Telescope (RCT) located at KPNO, Mc Cook and Guinan initiated a pilot program of carrying out high precision VRI CCD photometry. Test observations have been carried out during the Spring 2003 and the RCT is expected to acheive near-full operation during late 2003 or early 2004. This photometric program focuses on the study of variable stars in clusters. Selected astrophysically important eclipsing binaries, pulsating variables, blue stragglers, and chromospherically active variable stars will be studied. Also, searches of new variable stars will be made from the expected large samples of cluster stars. For example, photometry is planned of the several W UMa eclipsing binaries and blue straggler stars in the old open cluster NGC 188. Photometry also will be carried out of the young open cluster NGC 7790. This cluster is unique because has three confirmed classical cepheid members: CE Cas A (V $\sim +10.9$ mag; F8 Ib; P = 4.446 d ), CE Cep B (V $\sim +11.0$ mag; F9 Ib; 5.128 d), and CF Cas (V $\sim +11.1$ mag; F8 Ib; 4.875 d). NGC 7790 also contains the 10th mag eccentric B0+B0 eclipsing binary QX Cas. The observations of QX Cas are being conducted to determine the accurate distance to this star and thus to the cluster and its cepheid members. When complete these observations, combined with spectroscopy, will permit a reliable calibration of the ``zero-point'' of the galactic cepheid Period-Luminosity Law. Another possible project is the search of light variations of PMS stars and chromospherically active stars (from star spot rotational modulations) in young clusters such as the $\alpha$ Perseus Cluster, h & $\chi$ Per, M34, and the Pleiades.

Refurbishment of the RCT has been made possible by NASA grant NAG 58762. The RCT Consortium includes: Western Kentucky Univ., S. Carolina St Univ., Francis Marion Univ., Villanova Univ., and the Planetary Science Institute (PSI).