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Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement
Sun, Tiancheng Ge, Zhishuai Chen, Xunzhou Bi, Shaolan Li, Tanda Zhang, Xianfei Li, Yaguang Wu, Yaqian Bird, Sarah A. Ferguson, Jason W.
Sun, Tiancheng
Ge, Zhishuai
Chen, Xunzhou
Bi, Shaolan
Li, Tanda
Zhang, Xianfei
Li, Yaguang
Wu, Yaqian
Bird, Sarah A.
Ferguson, Jason W.
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2023-09
Type
Article
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Keywords
Stellar abundances,Stellar ages,Stellar kinematics,Milky Way disk,Fundamental parameters of stars
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Citation
Sun, T., Ge, Z., Chen, X., Bi, S., Li, T., Zhang, X., Li, Y., Wu, Y., Bird, S.A., Ferguson J.W., Zhou, J., Ye, L., Long, L., & Zhang, J. (2023). Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement. Astrophysical Journal, Supplement Series, 268(1), art. no. 29. https://doi.org/10.3847/1538-4365/ace5b0
Abstract
Varying oxygen abundance could impact modeling-inferred ages. This work aims to estimate the ages of dwarfs considering observed oxygen abundance. To characterize 67,503 LAMOST and 4006 GALAH FGK-type dwarf stars, we construct a grid of stellar models, which take into account oxygen abundance as an independent model input. Compared with ages determined with commonly used α-enhanced models, we find a difference of ~9% on average when the observed oxygen abundance is considered. The age differences between the two types of models are correlated to [Fe/H] and [O/α], and they are relatively significant on stars with [Fe/H] ≲ -0.6 dex. Generally, varying 0.2 dex in [O/α] will alter the age estimates of metal-rich (-0.2 < [Fe/H] < 0.2) stars by ~10% and relatively metal-poor (-1 < [Fe/H] < -0.2) stars by ~15%. Of the low-O stars with [Fe/H] < 0.1 dex and [O/α] ~-0.2 dex, many have fractional age differences of ~10% and even reach up to 27%. The fractional age difference of high-O stars with [O/α] ~0.4 dex reaches up to -33% to -42% at [Fe/H] ≲ -0.6 dex. We also analyze the chemical properties of these stars. We find a decreasing trend of [Fe/H] with ages from 7.5-9 Gyr to 5-6.5 Gyr for the stars from the LAMOST and GALAH. The [O/Fe] of these stars increases with decreasing age from 7.5-9 Gyr to 3-4 Gyr, indicating that the younger population is more O rich.
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Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Publisher
American Astronomical Society
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Series
Astrophysical Journal, Supplement Series
v.268 no. 11, art. no. 29
v.268 no. 11, art. no. 29
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DOI
ISSN
0067-0049