EDP Sciences
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Volume 368, Number 3, March IV 2001
Page(s) 880 - 887
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010043

A&A 368, 880-887 (2001)
DOI: 10.1051/0004-6361:20010043

Stability of pulsation of the double-mode high-amplitude $\delta$ Scuti star AE Ursae Majoris

M. D. Pócs and B. Szeidl

Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest, Hungary
    e-mail: pocs@konkoly.hu; szeidl@konkoly.hu

(Received 16 October 2000 / Accepted 4 December 2000 )

Stability of both the fundamental and first overtone oscillations of AE UMa was investigated by different methods which led to concordant results. The fundamental period of AE UMa has been essentially constant in the past 60 years consistent with the theoretical expectation (Breger & Pamyatnykh 1998). The reported fast period decrease (Hintz et al. 1997) is shown to be incorrect. The constancy of the fundamental period suggests that the star is in the post-main sequence evolutionary state as suggested by the evolutionary theories. The first overtone period is decreasing with a rate of $(1/P_1)
({\rm d}P_1/{\rm d}t)=-7.3 10^{-8} {\rm y}^{-1}$. The fact that the rate of period change for two modes is quite different indicates that non-evolutionary effects may also generate period changes. The changes in amplitude of the fundamental and first overtone were examined by comparing the least-squares amplitude solution for different segments of observations. Small long-term variations in the amplitudes have occurred in the past 25 years.

Key words: stars: oscillation -- stars: variables: $\delta$ Sct -- stars: individual: AE UMa

Offprint request: B. Szeidl, szeidl@konkoly.hu

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