BV PHOTOMETRY OF V9, THE ONLY RR LYRAE VARIABLE IN THE GLOBULAR-CLUSTER 47 TUCANAE

BV CCD photometry for the RR Lyrae variable V9 (HV 810) in the globular cluster 47 Tucanae is presented. Radial-velocity measurements indicate V9 is a cluster member while two other candidates, V12 (HV 814) and UX Tuc (HV 809) are not. A color-magnitude diagram is constructed from a subset of the 300 short-exposure CCD frames, showing V9 is unusually bright and hot relative to the red horizontal branch, and has an abnormally long pulsation period for its pulsational amplitude, both of which indicate it is highly evolved. There is also a suggestion of a ''spike'' in the light curve near phi almost-equal-to 0.08, which could be caused by the emergence of the echo of the prior minimum-radius pressure wave bouncing off the helium core. The photometry will be utilized in a subsequent Baade-Wesselink analysis.