Stability of pulsation of the double-mode high-amplitudeδScuti star AE Ursae Majoris

Abstract

Abstract. 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/P1)(dP1/dt) = −7.3 10 −8 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.

The beat-curve approach applied to AEUMa

“…Tables 1 and 2 give results for the quadratic fitting functions and the resulting calculated values of the periods and their rates of change. The most recent published results for the periods and their rates of change are by Pócs & Szeidl (2001), and in Table 3 we compare the rates of change of the periods from our study with those of these authors. We have quoted the most precise values of the periods given by Pócs & Szeidl (2001): in the case of P0 the value from their (O-C) method, and in the case of P1 from their fits to Fourier phase diagrams.…”

“…A study of the stability of the pulsation of AE UMa was published by Pócs & Szeidl (2001). They used Fourier methods, and non-beat-curve (O-C) analysis on previously published photometric data to conclude that the fundamental period had remained essentially constant in the past 60 years.…”

“…We have used the same times of maximum light for AE UMa as those given in Pócs & Szeidl (2001), apart from those based on visual or photographic observations. To these we have added data since published by Agerer & Hübscher (2003), Hübscher et al (2005) and Klingenberg et al (2006).…”

“…To these we have added data since published by Agerer & Hübscher (2003), Hübscher et al (2005) and Klingenberg et al (2006). We constructed beat curves for each observing season using the same elements as those given by Pócs & Szeidl (2001): C = 2442062.5824 + 0.08601707E, P b = 0.2936323 d. Figures 2 and 3 show the values of (O-C) (= B) and of δ as a function of time, together with quadratic fits made using singular value decomposition (SVD) with weighted points as described by Press et al (1992), and also piecewise-linear fits. The error bars in Figures 2 and 3 represent formal statistical errors.…”

“…Then we apply the beat-curve method to published times of maximum light for the double-mode pulsating star AE UMa, and compare the results with those obtained by Pócs & Szeidl (2001).…”