Spectroscopic mode identification for the β\,Cephei starEN (16) Lacertae

We perform for the first time spectroscopic mode identification in the eclipsing binary Cephei star EN (16) Lac. This mode identification is based upon a time series of 942 line profiles of the He I 6678 Å line in its spectrum. All three known frequencies 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 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 . Fits to the amplitude and phase variability of the modes imply a rotation frequency between 0.1 and 0.4 c d-1. The star's rotation axis is not aligned with the orbital axis.