2003A&A...399..639A

We perform for the first time spectroscopic mode identification in the eclipsing binary βCephei star EN(16) Lac. This mode identification is based upon a time series of 942 line profiles of the HeIλλ6678Å line in its spectrum. All three known frequencies f₁, f₂, f₃ of the star are present in the line-profile variations, but we failed to find additional modes. Using different identification methods we find conclusive evidence for the radial nature of the main mode and for the l=2, m=0 identification of the mode with frequency f₂. A unique identification of the third mode is not possible from the spectra, but we do derive that l₃<3. Fits to the amplitude and phase variability of the modes imply a rotation frequency between 0.1 and 0.4c/d. The star's rotation axis is not aligned with the orbital axis.