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Astron. Astrophys. 343, 872-882 (1999)


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Selection of a sample of bright southern Slowly Pulsating B Stars for long-term photometric and spectroscopic monitoring *

C. Aerts  **  1, P. DeCat 1, E. Peeters  ***  1, L. Decin  ****  1, J. De Ridder 1, K. Kolenberg[FORMULA]  1, G. Meeus 1, H. Van Winckel[FORMULA]  1, J. Cuypers 2 and C. Waelkens 1

1 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, B-3001 Heverlee, Belgium
2 Koninklijke Sterrenwacht van Belgiï, Ringlaan 3, B-1080 Brussels, Belgium

Received 6 October 1998 / Accepted 2 December 1998

Abstract

The photometric experiment on Hipparcos has led to the discovery of, among other types of variables, a large amount of new Slowly Pulsating B Stars. We have selected twelve bright southern stars of this sample, together with five previously known Slowly Pulsating B Stars, for spectroscopic and photometric monitoring. These seventeen stars have spectral types ranging from B 2 up to B 9 and thus fully cover the instability strip. We here present the results of a preliminary analysis of our data and show that our sample is an extremely important one to perform seismology of intermediate-massive stars.

In particular, we find that all but one of the selected stars exhibit clear line-profile variability. The broader-lined Slowly Pulsating B Stars tend to have more complex line-profile variations. One of the previously known Slowly Pulsating B stars was known to be a binary. Besides this star, another six of the selected Slowly Pulsating B stars turn out to be multiple systems. Five of these seven binaries have large rotational velocities and complicated line-profile variations with moving subfeatures. It is not yet clear whether or not the binarity results in a particular spectrum of excited modes.

Key words: stars: variables: general – stars: binaries: spectroscopic – stars: oscillations – stars: early-type

* Based on observations collected with the CAT Telescope of the European Southern Observatory and with the Swiss Photometric Telescope of the Geneva Observatory, both situated at La Silla in Chile
** Postdoctoral Fellow, Fund for Scientific Research, Flanders
*** Present Address: S.R.O.N. Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
**** Research Assistant, Fund for Scientific Research, Flanders

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999

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