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Fundamental Parameters of Main Sequence Turn-off Star Candidates Observed with the LAMOST and Kepler
Yaqian Wu (Beijing Normal University), Maosheng Xiang (National Astronomical Observatories), Tandai Li (National Astronomical Observatories), Shaolan Bi (Beijing Normal University), et al.
Main sequence turn-off (MSTO) stars are advantaged indictors of Galactic evo- lution since their ages could be robustly estimated based on atmospheric parameters. A few hundred of thousands of MSTO stars have been selected from the LAMOST Galactic surveys to study the structure and evolution of the Milky disk by Xiang et al. (2015). In this work, we validate the age estimates, as well as examine the contamination rate of the MSTO sample of Xiang et al. with a sample of 179 stars that have asteroseismic parameters from analysis of the Kepler photometry. We determine accurate fundamental stellar parameters (M, R, Age, L, Teff, Z, log g) for 150 stars by combing the asteroseismic properties Δ, max and stellar atmospheric parameters yielded by the LSP3 from LAMOST spectra, utilizing a dense grid of evolutionary tracks we constructed. We find that for the majority of stars, the age esti- mates of Xiang et al. are basically consistent with our results, with a mean difference and standard deviation of 0.53 and 2.71 Gyr, respectively. Nevertheless, according to our results, a considerable fraction of the MSTO stars in Xiang et al’s sample are prob- ably contaminations from either main sequence stars or sub giant stars, and ages for many of those contamination stars could be significantly overestimated. The contamination rate is especially higher for the older stars. The main cause of the high fraction of contaminations is the relatively large systematic bias of surface gravity yielded by the current LSP3.