G. Scholz

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 from four observatories and of 994 radial velocities (RV hereafter) from photographic spectra, published by several authors, has allowed us to disentangle the RV variations due to orbital motion and due to pulsations of the star. New, accurate orbital elements as well as precise values of the three pulsation periods, already known from the previous studies, were derived. The accuracy of the orbital solution has been substantially improved after the observed RV changes were properly prewhitened for the short-term oscillations. The amplitude of the dominant RV oscillation with a period of P_1=0fd16916703 was found to vary with a 74 year cycle. The amplitudes of the two other RV oscillations, having periods of P_3=0fd 18173256 and P_2=0fd 17085554, vary on much shorter time scales of 674 d and 331 d, respectively. The value of P_2 derived here does not correspond to a one year alias of the value found by several authors from photometry but appears to be an 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 the first time we present evidence of line profile variations of EN Lac. They correlate well with the short-term RV variations but they alternatively occur with periods corresponding either to the fundamental periods or to the first harmonics of P_1 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 the stars are approaching periastron. Since this could be a signature of forced oscillations, the effect is worth further study, though it appears rather marginal at present.

HD 169981 -an overlooked photometric binary?

In 1999 and 2000 we obtained spectroscopic and photometric observations of the A-type binary star HD 169981. The observations were part of a campaign to search for short-term photometric and radial-velocity variations among early-type binaries. From the radial velocities of 18 metal lines we derived more precise orbital elements. Quite unexpectedly, our photometric data show a dip that could be caused by an eclipse. The same feature is also visible in the Hipparcos data. From our analysis of the available observations we have estimated the physical parameters of the binary. Neither the spectroscopic nor the photometric observations hint at any short-term variations.

Binary nature and elemental abundances of 2 Lyn and HD 169981

We analyse high-resolution spectrograms of the early A-type stars HD 169981 and 2 Lyn. For the spectroscopic and photometric binary HD 169981 we determine the abundances of certain chemical elements. The derived atmospheric parameters show the star to be an A giant. The abundances of the elements Mg, Si, Ti, Cr, and Fe are very close to solar, only C and O show slight underabundances. 2 Lyn has been primarily studied for the occurrence of radial velocity variations. The star is probably a spectroscopic binary with a period of about 3.6 years. Preliminary orbital elements are derived. The search for shorter radial velocity variations gives hints of periods of 69.2, 1.56 and 1.53 days. Both of the last-mentioned periods are in the order of the expected rotation period of the star. The stellar parameters are estimated and for certain elements we determined the abundances.