β Cephei Pulsations in the High-mass Eclipsing System 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 Transiting Exoplanet Survey Satellite 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_⊙ and 11.88 M_⊙ and radii of 5.52 R_⊙ and 5.09 R_⊙ in an eccentric orbit of e = 0.0305. The distance to the eclipsing system, 928 ± 36 pc, is much more precise than the Gaia distance of 962 ± 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 β Cep-type pulsations. Our results represent the second discovery of β 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.