Searching for Variability in the Blue Straggler Star Region of the Globular Cluster NGC 6397

Abstract We studied stellar variability in the subgiant branch and blue straggler stars region of the globular cluster NGC 6397. The aim of this research is to identify and characterize new short-period, low-amplitude variable stars. We analyzed 469 stars using periodograms generated by the statistical methods phase dispersion minimization and generalized Lomb–Scargle, and a significance test. In total, eight variables were identified in this investigation. These variables exhibit periods in the range 0.03 < P V < 0.5 days and optical amplitudes below 0.2 mag, with light-curve shapes similar to those previously reported. Notably, two of the identified variables show very short periods, below 0.04 days. We also confirmed the cluster membership of these variables and grouped them according to the shape of their light curves. Additionally, we reanalyzed a previously cataloged eclipsing variable star, initially reported with a period of 0.78669 days, and obtained an improved period of 0.29419 days, suggesting a revised classification.