Spectroscopic and photometric investigations of MAIA candidate stars

Abstract

Including our own observational material and the Hipparcos photometry data, we investigate the radial velocity and brightness of suspected Maia variable stars which are classified also in some examples as peculiar stars, mainly for the existence of periodic variations with time-scales of hours. The results lead to the following conclusions: (1) Short-term radial velocity variations have been unambiguously proved for the A0 V star gamma CrB and the A2 III star gamma UMi. The stars pulsate in an irregular manner. Moreover, gamma CrB shows a multiperiod structure quite similar to some of the best-studied neighbouring delta Scu 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 Hipparcos data confirm a short-period variation found already earlier. Furthermore, we find changes of the colour index in theta Vir and gamma CrB on a time-scale of days. (3) No proofs for the existence of a separate 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 Hertzsprung-Russell diagram, our observational runs are too short and the accuracy of the measurements too low to exclude such pulsations in the other 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.

Based on spectroscopic observations taken with the 2 m telescope at the Thüringer Landessternwarte.