Ages of 70 dwarfs of three populations in the solar neighborhood: considering O and C abundances in stellar models
Ge, Z. S.
Bi, S. L.
Chen, Y. Q.
Li, T. D.
Zhao, J. K.
Ferguson, Jason W.
Wu, Y. Q.
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Ge, Z. S.; Bi, S. L.; Chen, Y. Q.; Li, T. D.; Zhao, J. K.; Liu, K.; Fergusion, Jason W.; Wu, Y. Q. 2016. Ages of 70 dwarfs of three populations in the solar neighborhood: considering O and C abundances in stellar models. Astrophysical Journal, vol. 833:no. 2
Oxygen and carbon are important elements in stellar populations. Their behavior refers to the formation history of the stellar populations. C and O abundances would also obviously influence stellar opacities and the overall metal abundance Z. With observed high-quality spectroscopic properties, we construct stellar models with C and O elements to give more accurate ages for 70 metal-poor dwarfs, which have been determined to be high-a halo, low-alpha halo, and thick-disk stars. Our results show that high-alpha halo stars are somewhat older than low-alpha halo stars by around 2.0 Gyr. The thick-disk population has an age range in between the two halo populations. The age distribution profiles indicate that high-alpha halo and low-alpha halo stars match the in situ accretion simulation by Zolotov et al., and the thick-disk stars might be formed in a relatively quiescent and long-lasting process. We also note that stellar ages are very sensitive to O abundance, since the ages clearly increase with increasing [O/Fe] values. Additionally, we obtain several stars with peculiar ages, including 2 young thick-disk stars and 12 stars older than the universe age.
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