Photometric Analysis of Variable Stars in NGC 6397

Abstract This study investigates a population of low-amplitude, short-period variable stars in the globular cluster NGC 6397, specifically targeting those stars between 11 and 15 mag in the V band. We combined the generalized Lomb–Scargle and phase dispersion minimization periodograms to analyze 592 light curves across V and I filters. Through the application of stringent criteria, we determined the periodicity and amplitude consistency, identifying 51 candidates as potential variable stars. Following a significance test, the sample was refined to 26 giants, classifying 18 as variables, 7 as possible variables, and 1 as dubious. We also confirmed the cluster membership of these candidates and categorized each based on the morphology of their light curves. The variables identified exhibit periods ranging from 0.0389 to 0.5500 days and amplitudes between 0.0058 and 0.1168 mag, offering new insights into stellar behavior within NGC 6397.