AE Ursae Majoris – a δ Scuti star in the Hertzsprung Gap

Abstract We analyse the photometric data and spectroscopic data collected on the δ Scuti star AE Ursae Majoris (AE UMa). The fundamental and the first overtone frequencies are confirmed as f 0 = 11.625 60 c d−1 and f 1 = 15.031 24 c d−1, respectively, from the frequency content by analysing light curves over 40 nights, spanning from 2009 to 2012. Additionally, another 37 frequencies are identified as either the harmonics or the linear combinations of the fundamental and the first overtone frequencies, among which 25 are newly detected. The rate of period change of the fundamental mode is determined as (1/P 0)(dP 0/dt) = 5.4(±1.9) × 10−9 yr−1 as revealed from the O − C diagram based on the 84 newly determined times of maximum light combined with those derived from the literature. The spectroscopic data suggest that AE UMa is a Population I δ Scuti star. With these physical properties, we perform theoretical explorations based on the stellar evolution codemesa on this target, considering that the variation of pulsation period is caused by secular evolutionary effects. We finally constrain AE UMa with physical parameters as follows: mass of 1.805 ± 0.055 M⊙, radius of 1.647 ± 0.032 × 1011 cm, luminosity of 1.381 ± 0.048(log L/L⊙) and age of 1.055 ± 0.095 × 109 yr. AE UMa can be the (Population I) δ Scuti star that locates just after the second turn-off of its evolutional track leaving the main sequence, a star in the phase of the Hertzsprung Gap with a helium core and a hydrogen-burning shell.