STELLAR VARIABILITY IN THE CENTRAL POPULATIONS OF 47-TUCANAE FROM WF PC OBSERVATIONS WITH THE HUBBLE-SPACE-TELESCOPE .1. PROJECT OVERVIEW, REDUCTION TECHNIQUES, AND FIRST RESULTS

Stars in the central region of the dense globular cluster 47 Tucanae were monitored for variability using time-resolved photometry from 99 Hubble Space Telescope Planetary Camera exposures of 1000 s in the F336W (U) filter. The observations were obtained while 47 Tuc was in the continuous viewing zone (CVZ) of HST. This data set provides an unparalleled sensitivity for quantification of stellar variability: (1) in the blue straggler population, delta Scuti oscillations would provide important constraints on these enigmatic stars; (2) studies of cataclysmic variables detectable through dwarf novae outbursts or orbital modulation are of interest in testing formation theories; (3) eclipsing binaries and W UMa Systems are of fundamental interest for cluster dynamics considerations. In this paper the unique data analysis challenges posed in following some 20,000 (undersampled PSF cores with extended spherical aberration induced halos) stars with near-Poisson limited precisions given the complications of image motion and a high rate of cosmic rays are addressed in detail. Examples of the oscillating blue stragglers, eclipsing binaries, and near-contact binary systems detected in this project are discussed.