A new analysis of the radial velocity variations of the eclipsing and spectroscopic binary EN Lacertae

An analysis of 1236 new electronic spectra of the eclipsing binary EN Lac f rom four observatories and of 994 radial velocities (RV hereafter) from pho tographic spectra, published by several authors, has allowed us to disentan gle the RV variations due to orbital motion and due to pulsations of the st ar. New, accurate orbital elements as well as precise values of the three p ulsation periods, already known from the previous studies, were derived. Th e accuracy of the orbital solution has been substantially improved after th e observed RV changes were properly prewhitened for the short-term oscillat ions. The amplitude of the dominant RV oscillation with a period of P-1 = 0 (d).16916703 was found to vary with a 74 year cycle. The amplitudes of the two other RV oscillations, having periods of P-3 = 0(d).18173256 and P-2 = 0(d).17085554, vary on much shorter time scales of 674 d and 331 d, respect ively. The value of P-1 derived here does not correspond to a one year alia s of the value found by several authors from photometry but appears to be a n intrinsic period. The time scales of the amplitude modulations found for P-1 and P-3 are in good agreement with previous photometric results. For th e first time we present evidence of line profile variations of EN Lac. They correlate well with the short-term RV variations but they alternatively oc cur with periods corresponding either to the fundamental periods or to the first harmonics of A to P-3 An analysis of the RV scatter along the orbital phase curve for the new spectra, obtained over a relatively short interval of time, gives some indication of a sharp increase of this scatter when th e stars are approaching periastron. Since this could be a signature of forc ed oscillations, the effect is worth further study, though it appears rathe r marginal at present**.