$\beta$ Cephei Pulsations in the High-mass Eclipsing System CW Cephei

TL;DR

This paper reports the discovery of $eta$ Cephei pulsations in the high-mass eclipsing binary CW Cephei using TESS data, providing precise stellar parameters and new insights into high-mass star pulsations.

Contribution

It is the first detailed analysis of $eta$ Cephei pulsations in a high-mass eclipsing binary with precisely measured stellar parameters.

Findings

Detected 13 significant signals in the light curve.

Identified 7 frequencies as $eta$ Cep-type pulsations.

Provided precise stellar masses and radii for CW Cephei.

Abstract

CW Cep is an early B-type eclipsing binary with mass measurement precisions better than 1 \%. We report the discovery of pulsation signatures in the TESS time-series data of the system observed during Sectors 17 and 18. Our binary modeling indicates that the target star is a partially-eclipsing detached system with masses of 12.95 $M_\odot$ and 11.88 $M_\odot$ and radii of 5.52 $R_\odot$ and 5.09 $R_\odot$ in an eccentric orbit of $e$ = 0.0305. The distance to the eclipsing system, 928 $\pm$ 36 pc, is much more precise than the Gaia distance of 962 $\pm$ 453 pc. Applying multifrequency analyses to the residual light curve in the outside-eclipse part, we detected 13 significant signals in two frequency regions. Six frequencies below 1 day$^{-1}$ appeared to be mostly orbital harmonic and combination terms, or sidelobes due to insufficient removal of the binary effects. In contrast, seven frequencies clustered around 2.73 day$^{-1}$ and 5.34 day$^{-1}$ could be considered $\beta$ Cep-type pulsations. Our results represent the second discovery of $\beta$ Cep pulsations present in double-lined eclipsing binaries with precise masses and, hence, CW Cep serves as an important test-bed for the asteroseismic modeling of high-mass stars.