Period Changes of LMC Cepheids in the OGLE and MACHO Data

Understand

Pulsation period of Cepheids should change as stars evolve through the instability strip.

• Rates of these changes found by other authors based on the decades-long O-C diagrams show rather good agreement with theoretical predictions.
• We have checked the variability on the scale of a few years on the data recently published by the Optical Gravitational Lensing Experiment (OGLE) for the Large Magellanic Cloud Cepheids and found period changes for 18% of fundamental mode and 41% of first overtone pulsators.
• It suggest the overtone pulsations are less stable than the fundamental ones.