Search for Evolutionary Changes in the Periods of Cepheid: DX Gem

Abstract

For the low-amplitude Cepheid DX Gem we have constructed an O - C diagram spanning a time interval of 120 years. The O - C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, dP/dt = −0.808(±0.108) s yr⁻¹, which points to the second crossing of the instability strip. The available data reduced by the Eddington-Plakidis method show random period fluctuations, ε/P ≈ 0.0072, whose amplitude on the O - C diagram is comparable to the amplitude of evolutionary changes.