Pulsation and Rotation of the EL CVn-type Eclipsing Binary 1SWASP J024743.37-251549.2

Abstract

EL CVn-type eclipsing binaries are composed of a massive A-type main-sequence primary star and a hotter B-type secondary star. This paper presents the time-series photometric and asteroseismic results of the EL CVn-type star 1SWASP J024743.37-251549.2. Well-defined eclipsing light curves were constructed by using the novel high-cadence BV data and archival TESS data, and the physical parameters of each binary component were derived by modeling the light curves. Multiple frequency analysis was performed to investigate the pulsation properties of the binary components. A reliable signal could not be detected in the high-frequency region of 100-300 day −1 , unlike in the previous discovery of three frequencies around 200 day −1 . This indicates that the pulsation amplitudes of the pre-helium white dwarf secondary component decreased considerably. By contrast, 12 frequencies were detected in the range of 33 to 53 day −1 . Most of them were classified as δ Sct-type pulsations originating from the primary star. Theoretical frequencies for the seismic analysis were obtained by adding the non-rotating model frequencies from the GYRE and their rotational shifts from the complete calculation approach. Grid-based fitting was conducted for various stellar properties. The theoretical frequencies and stellar parameters of the best solution concurred well with the observations. The rotation rate was constrained to 1.50 ± 0.02 day −1 , indicating the synchronized rotation of the primary star. The results imply that the complete approach based on the polytropic model is applicable to the seismic analysis of fast-rotating δ Sct stars.