CCD Observations of the RR Lyrae Variables in the Globular Cluster NGC 5897

Abstract

CCD observations for 10 (six previously known and four newly discovered) of the 11 RR Lyrae variables in NGC 5897 have been analyzed. The period-luminosity and period-amplitude plots indicate that the population of RR Lyrae variables in NGC 5897 includes three fundamental mode, four first-overtone and four second-overtone variables with mean periods 0.828, 0.459, and 0.343 days, respectively. The variables have properties similar to some of the Oosterhoff type II variables in ω Centauri. Two of the new variables (V11 and V13) were previously considered to be possible nonvariables that lie within or near the instability strip on the horizontal branch; both have V amplitudes less than 0.2 mag. There is a chance that one or two of the variables (V10 and possibly V3) might be anomalous Cepheids and not RR Lyrae stars.