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Astron. Astrophys. 337, 447-459 (1998)


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Spectroscopic and photometric investigations of MAIA candidate stars *

G. Scholz 1, H. Lehmann 2, G. Hildebrandt 1, K. Panov 3 and L. Iliev 3

1 Astrophysikalisches Institut Potsdam, Telegrafenberg A27, D-14473 Potsdam, Germany (gscholz@aip.de, ghildebrandt@aip.de)
2 Thüringer Landessternwarte Tautenburg, D-07778 Tautenburg, Germany (lehm@tls-tautenburg.de)
3 Institute of Astronomy, Sofia, Bulgarian Academy of Sciences, Bulgaria (kpanov@bgearn.acad.bg, liliev@bgearn.acad.bg)

Received 5 January 1998 / Accepted 22 June 1998

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 [FORMULA] CrB and the A2 III star [FORMULA] UMi. The stars pulsate in an irregular manner. Moreover, [FORMULA] CrB shows a multiperiod structure quite similar to some of the best-studied neighbouring [FORMULA] 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, [FORMULA] Vir, [FORMULA] UMi, and [FORMULA] CrB. For ET And the Hipparcos data confirm a short-period variation found already earlier. Furthermore, we find changes of the colour index in [FORMULA] Vir and [FORMULA] 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 [FORMULA] CrB and [FORMULA] 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 [FORMULA] 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 [FORMULA] Gem, [FORMULA] Vir, [FORMULA] Dra, 4 Lac, and ET And give no evidence of the presence of longitudinal magnetic field strengths larger than about 150 gauss.

Key words: binaries: spectroscopic – stars: early-type – stars: magnetic fields – stars: oscillations

* Based on spectroscopic observations taken with the 2 m telescope at the Thüringer Landessternwarte Tautenburg, Germany, and with the 2 m telescope of the National Astronomical Observatory Rozhen, Bulgaria. For photometric investigations we used the 0.6 m telescope at Rozhen and the Hipparcos and Tycho catalogues.

Send offprint requests to: G. Scholz

© European Southern Observatory (ESO) 1998

Online publication: August 17, 1998

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