2017AJ....153..102D

In this work, the relation between the period change and evolutionary status of SW Tau, a Type II Cepheid variable, is examined. An (O-C) analysis of the times of maxima of SW Tau has been undertaken to determine this relation. SW Tau has the characteristic light curve shape of BL Her type stars. By taking into consideration SW Tau's well-defined period decrease, obtained from the photometric observations, its position on the HR diagram in accordance with evolutionary models, and its chemical composition, we demonstrate that SW Tau is a Cepheid crossing the instability strip for the fourth time. SW Tau could be interpreted as being an early AGB star on the blueward evolutionary phase during shell helium burning.