SPECTROSCOPIC AND PHOTOMETRIC INVESTIGATIONS OF MAIA CANDIDATE STARS

Including our own observational material and the Hipparcos photometry data, we investigate the radial velocity and brightness of suspected M aia variable stars which are classified also in some examples as pecul iar stars, mainly for the existence of periodic variations with time-s cales of hours. The results lead to the following conclusions: (1) Sho rt-term radial velocity variations have been unambiguously proved for the A0 V star gamma CrB and the A2 III star gamma UMi. The stars pulsa te in an irregular manner. Moreover, gamma CrB shows a multiperiod str ucture quite similar to some of the best-studied neighbouring delta Sc u stars. (2) In the Hipparcos photometry as well as in our photometric runs we find significant short- and long-term variations in the stars HD 8441, 2 Lyn, theta Vir, gamma UMi, and gamma CrB. For ET And the H ipparcos data confirm a short-period variation found already earlier. Furthermore, we find changes of the colour index in theta Vir and gamm a CrB on a time-scale of days. (3) No proofs for the existence of a se parate class of variables, designated as Maia variables, are found. If the irregular behaviour of our two best-investigated stars gamma CrB and gamma UMi is typical for pulsations in this region of the Hertzspr ung-Russell diagram, our observational runs are too short and the accu racy of the measurements too low to exclude such pulsations in the oth er stars, however. (4) The radial velocities of the binaries alpha Dra and ET And have been further used for a recalculation of the orbital elements. For HD 8441 and 2 Lyn we estimated the orbital elements for the first time. (5) Zeeman observations of the stars gamma Gem, theta Vir, alpha Dra, 4 Lac, and ET And give no evidence of the presence of longitudinal magnetic field strengths larger than about 150 gauss.