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 w ere monitored for variability using time-resolved photometry from 99 H ubble Space Telescope Planetary Camera exposures of 1000 s in the F336 W (U) filter. The observations were obtained while 47 Tuc was in the c ontinuous viewing zone (CVZ) of HST. This data set provides an unparal leled sensitivity for quantification of stellar variability: (1) in th e blue straggler population, delta Scuti oscillations would provide im portant constraints on these enigmatic stars; (2) studies of cataclysm ic variables detectable through dwarf novae outbursts or orbital modul ation are of interest in testing formation theories; (3) eclipsing bin aries and W UMa Systems are of fundamental interest for cluster dynami cs considerations. In this paper the unique data analysis challenges p osed in following some 20,000 (undersampled PSF cores with extended sp herical aberration induced halos) stars with near-Poisson limited prec isions given the complications of image motion and a high rate of cosm ic rays are addressed in detail. Examples of the oscillating blue stra gglers, eclipsing binaries, and near-contact binary systems detected i n this project are discussed.