* Astronomy

Title: AE Ursae Majoris -- a delta Scuti Star in the Hertzsprung Gap
Author: Jia-Shu Niu, Jian-Ning Fu, Yan Li, Xiao-Hu Yang, Weikai Zong, Hui-Fang Xue, Yan-Ping Zhang, Nian Liu, Bing Du, Fang Zuo

We analyze the photometric data and spectroscopic data that collect on the delta Scuti star AE UMa. The fundamental and the first overtone frequencies are confirmed as f0=11.62560\,c\,d^-1 and f1=15.03124\,c\,d^-1, respectively, from the frequency content by analysing of the 40 nights light curve 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/P0)(dP0/dt)=5.4(±1.9) x 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 suggests that AE UMa is a population,I delta Scuti star. With these physical properties, we perform theoretical explorations based on the stellar evolution code MESA on this target, considering that the variation of pulsation period is caused by secular evolutionary effects. We finally constraint the AE UMa with the physical parameters as: the mass of 1.805±0.055 solar masses, the radius of 1.647±0.032 x 10^11cm, the luminosity of 1.381±0.048 (logL/solar luminosity) and the age of 1.055±0.095 x 10^9 yr. AE UMa can be the (Pop. I) delta 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.

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