Period and amplitude variations in the high-amplitude δ Scuti star AE Ursae Majoris

We present a comprehensive investigation of the variations of period and amplitude in the high-amplitude delta Scuti star AE UMa based on our new Johnson V time-series measurements and the existing data. No additional frequencies were detected even though all the available data sets from 1974 to 2001 were analysed. The light variations of AE UMa can be well-reproduced with the fundamental and first-overtone radial modes and their coupled terms. New observations and analyses support the most recent results of Pocs & Szeidl (2001). The fundamental period was essentially constant over the past 27 years with its standard value of 0.(d)086017066 (f(0) = 11.625600 cd(-1)), while the first overtone period decreased at a rate of 1/P-1 dP(1)/dt = -4.3 x 10(-8) yr(-1). The amplitude variations in the two modes of AE UMa are detected at the milli-magnitude level on a time-scale of years. It seems that the amplitudes vary in opposite phases, implying an energy conservation or some kind of intrinsic variability cause. We deny the over-interpretation of the period change given by Hintz et al. (1997) and explore its reason.