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Astron. Astrophys. 330, 605-611 (1998)


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Pulsation of the [FORMULA] Bootis stars HD 111786 and HD 142994 *

E. Paunzen 1, W.W. Weiss 1, P. Martinez 2, J.M. Matthews 3, A.A. Pamyatnykh 4, 5 and R. Kuschnig 1

1 Institut für Astronomie der Universität Wien, Türkenschanzstr. 17, A-1180 Wien, Austria (last_name@galileo.ast.univie.ac.at)
2 South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa (peter@peter.saao.ac.za)
3 Department of Physics & Astronomy, University of British Columbia, V6T 1Z4, Vancouver, Canada (matthews@astro.ubc.ca)
4 Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, PL-00 716 Warsaw, Poland (alosza@camk.edu.pl)
5 Institute of Astronomy, Russian Academy of Sciences, Pyatniskaya Str. 48, 109017 Moscow, Russia

Received 20 May 1997 / Accepted 19 September 1997

Abstract

The detection of possible nonradial pulsation modes among some [FORMULA] Bootis stars offers the prospect of using asteroseismology to determine their masses and ages, thereby testing competing theories for the origin of their chemical peculiarities. As a step toward this goal, we conducted multi-site photometric campaigns spanning two weeks each for two [FORMULA] Bootis stars already known to show oscillations with periods from 0.75 to 4 hr: HD 111786 and HD 142994. Comparison of the observed eigenfrequency spectrum with model eigenmode spectra can constrain the age of the star. Since two of the main proposed mechanisms for the [FORMULA] Bootis phenomenon (mass loss coupled with diffusion, and accretion) predict widely different stellar ages, such an analysis could distinguish between these options.

Frequency analysis of campaign data yielded four frequencies for each program star. The best matches of our observed eigenfrequencies to Main Sequence stellar models (which include the effects of rotation on the stellar structure and the pulsation modes) suggest that both stars are too far from the Zero-Age Main Sequence, to be consistent with the widely favoured accretion scenario. However, we caution that the results are preliminary and suggest future observing strategies to confirm/deny this finding.

Key words: stars: early type; oscillations; variables; ffi Sct; individual: HD 111786; HD 142994

* Based on observations obtained at CTIO, SAAO and with the Hipparcos satellite

Send offprint requests to: E. Paunzen

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
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