Publication Date:
2014-12-29
Description:
We intend to use stellar models with and without α-enhancement, as well as asteroseismic analysis, to study two α-enhanced stars, KIC 7976303 and KIC 8694723. For the α-enhanced models, we adopt [α/Fe] = 0.2 and 0.4. For the evolved subgiant KIC 7976303 with mixed modes, the α-enhanced models fit the observations better than the models without α-enhancement, and point to a star with M = 1.20 ± 0.02 M , t = 4.88 ± 0.08 Gyr, R = 2.04 ± 0.01 R and L = 5.07 ± 0.05 L . For the post turn-off star KIC 8694723, we find that the models fit the observations well in all three cases ([α/Fe] = 0.0, 0.2 and 0.4). According to the observed metal abundances, only α-enhanced models are used to estimate the stellar parameters, which are M = 1.13 ± 0.06 M , t = 5.47 ± 0.43 Gyr, R = 1.55 ± 0.13 R and L = 3.18 ± 0.26 L . Our α-enhanced models indicate that KIC 7976303 has a larger mass and younger age than in previous works based on standard models. Furthermore, the differences of estimated mass and age between the three cases are ~0.1 M and ~0.5–1.3 Gyr. These results suggest that we include α-enhancement in the modelling of α-enhanced stars, such as members of globular clusters and metal-poor stars in the disc and in the halo.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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