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

TL;DR

This study analyzes the pulsation and rotation of the EL CVn-type eclipsing binary 1SWASP J024743.37-251549.2 using photometric and asteroseismic data, revealing primary star pulsations and synchronized rotation.

Contribution

It introduces a comprehensive seismic analysis method combining GYRE models and rotational shifts, applied to a fast-rotating $\delta$ Sct star in an eclipsing binary.

Findings

Detected 12 $\delta$ Sct pulsation frequencies from the primary star.

Constrained the primary star's rotation rate to 1.50 $\pm$ 0.02 day$^{-1}$.

Found decreased pulsation amplitudes in the secondary star.

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 {\it 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 $\delta$ 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 $\pm$ 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 $\delta$ Sct stars.