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Astron. Astrophys. 349, 225-235 (1999)

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30+ frequencies for the [FORMULA] Scuti variable 4 Canum Venaticorum: results of the 1996 multisite campaign

M. Breger 1, G. Handler 1, R. Garrido 2, N. Audard 1, W. Zima 1, M. Paparó 3, F. Beichbuchner 1, Li Zhi-ping 4, Jiang Shi-yang 4, Liu Zong-li 4, Zhou Ai-ying 4, H. Pikall 1, A. Stankov 1, J.A. Guzik 5, M. Sperl 1, J. Krzesinski 6, W. Ogloza 6, G. Pajdosz 6, S. Zola 6,7, T. Thomassen 8, J.-E. Solheim 8, E. Serkowitsch 1, P. Reegen 1, T. Rumpf 1, A. Schmalwieser 1 and M.H. Montgomery 1

1 Astronomisches Institut der Universität Wien, Türkenschanzstrasse 17, A-1180 Wien, Austria (breger@astro.univie.ac.at)
2 Instituto de Astrofisica de Andalucia, CSIC, Apdo. 3004, E-18080 Granada, Spain
3 Konkoly Observatory, Box 67, H-1525 Budapest XII, Hungary
4 Beijing Observatory, Academy of Sciences, Beijing, P.R. China
5 Los Alamos National Laboratory, XTA, MS B220, Los Alamos, NM 87545, USA
6 Mt. Suhora Observatory, Cracow Pedagogical University, PL-30-083 Cracow, Poland
7 Jagiellonian University, U1. Orla 171 PL-30-244 Cracow, Poland
8 Department of Physics, University of Tromso, N-9037 Tromso, Norway

Received 8 April 1999 / Accepted 9 July 1999

Abstract

The evolved [FORMULA] Scuti variable 4 CVn was observed photometrically for 53 nights on three continents. We found a total of 34 significant and 1 probable simultaneously excited frequencies. Of these, 16 can be identified as linear combinations of other frequencies. All significant frequencies outside the 4.5 to 10 cd-1 (52 to 116 µHz) range can be identified with frequency combinations, fi [FORMULA] fj, of other modes with generally high amplitudes. There exists a number of closely spaced frequencies with separations of [FORMULA] 0.06 cd-1. This cannot be explained in terms of amplitude variability.

The results show that even for stars on and above the main sequence other than the Sun, a very large number of simultaneously excited nonradial oscillations can be detected by conventional means.

Since all pulsation modes with photometric amplitudes of 1 mmag or larger have now been detected for this star, a presently unknown mode selection mechanism must exist to select between the 1000+ of low-degree modes predicted to be excited for this (and many other) stars.

Phase differences and amplitude ratios between the y and v colors are determined for the ten main modes. The phase differences indicate p1 to p4 modes of [FORMULA] = 1 for four of these modes.

The formulae to determine the uncertainties in the amplitudes and phases of sinusoidal fits to observational data are derived in the Appendix.

Key words: stars: variables: ffi Sct – stars: oscillations – stars: individual: AI CVn – stars: individual: 4 CVn

Send offprint requests to: M. Breger

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© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999
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