Search for Evolutionary Changes in the Periods of Cepheids: BG Cru

Abstract

For the low-amplitude Cepheid BG Cru we have constructed an O - C diagram spanning a time interval 118 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 = −0.0787 (±0.0230) s yr⁻¹. This points to the second crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen (1993) confirms that the period decrease is real.