Mass and age of red giant branch stars observed with LAMOST and Kepler

Wu, Yaqian; Xiang, Maosheng; Bi, Shaolan; Liu, Xiaowei; Jiang, Yu; Hon, Marc; Sharma, Sanjib; Li, Tanda; Huang, Yang; Liu, Kang; Zhang, Xianfei; Li, Yaguang; Ge, Zhishuai; Tian, Zhijia; Zhang, Jinghua; Zhang, Jianwei

doi:10.1093/mnras/stx3296

Cited by 50 publications

(82 citation statements)

References 70 publications

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“…More sophisticated comparisons with GCE models are beyond the scope of this work, but will be addressed in future work. Figure 7 is in general agreement with similar figures using LAMOST data in Xiang et al (2017) and Wu et al (2018). Although these [α/M] vs [M/H] distribution are more extended, the age evolution is quite smooth.…”

Section: [M/h]-[α/m]-age Distributionsupporting

confidence: 89%

Spatial variations in the Milky Way disc metallicity–age relation

Feuillet

Frankel

Lind

et al. 2019

Monthly Notices of the Royal Astronomical Society

104

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Stellar ages are a crucial component to studying the evolution of the Milky Way. Using Gaia DR2 distance estimates, it is now possible to estimate stellar ages for a larger volume of evolved stars through isochrone matching. This work presents [M/H]age and [α/M]-age relations derived for different spatial locations in the Milky Way disc. These relations are derived by hierarchically modelling the star formation history of stars within a given chemical abundance bin. For the first time, we directly observe that significant variation is apparent in the [M/H]-age relation as a function of both Galactocentric radius and distance from the disc mid-plane. The [M/H]-age relations support claims that radial migration has a significant effect in the plane of the disc. Using the [M/H] bin with the youngest mean age at each radial zone in the plane of the disc, the present-day metallicity gradient is measured to be −0.059 ± 0.010 dex kpc −1 , in agreement with Cepheids and young field stars. We find a vertically flared distribution of young stars in the outer disc, confirming predictions of models and previous observations. The mean age of the [M/H]-[α/M] distribution of the solar neighborhood suggests that the high-[M/H] stars are not an evolutionary extension of the low-α sequence. Our observational results are important constraints to Galactic simulations and models of chemical evolution.

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Section: [M/h]-[α/m]-age Distributionsupporting

confidence: 89%

Spatial variations in the Milky Way disc metallicity–age relation

Feuillet

Frankel

Lind

et al. 2019

Monthly Notices of the Royal Astronomical Society

104

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“…The long trail of metal-rich stars (if not all stars within this oldest bin) are likely to have originated from the inner Galaxy. Qualitatively, the GALAH MDFs agree well with those of LAMOST presented in Wu et al (2018) (middle column of their figure 13), including a sub-solar peak for the youngest bins and an unsymmetrical MDF for the oldest bin.…”

Section: Implications For Radial Migrationsupporting

confidence: 77%

The GALAH survey: temporal chemical enrichment of the galactic disc

Lin

Asplund

Ting

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present isochrone ages and initial bulk metallicities ([Fe/H] bulk , by accounting for diffusion) of 163,722 stars from the GALAH Data Release 2, mainly composed of main sequence turn-off stars and subgiants (7000K > T eff > 4000K and logg > 3 dex). The local age-metallicity relationship (AMR) is nearly flat but with significant scatter at all ages; the scatter is even higher when considering the observed surface abundances. After correcting for selection effects, the AMR appear to have intrinsic structures indicative of two star formation events, which we speculate are connected to the thin and thick disks in the solar neighborhood. We also present abundance ratio trends for 16 elements as a function of age, across different [Fe/H] bulk bins. In general, we find the trends in terms of [X/Fe] vs age from our far larger sample to be compatible with studies based on small (∼ 100 stars) samples of solar twins but we now extend it to both sub-and super-solar metallicities. The α-elements show differing behaviour: the hydrostatic α-elements O and Mg show a steady decline with time for all metallicities while the explosive α-elements Si, Ca and Ti are nearly constant during the thin disk epoch (ages < ∼ 12 Gyr). The s-process elements Y and Ba show increasing [X/Fe] with time while the r-process element Eu have the opposite trend, thus favouring a primary production from sources with a short time-delay such as core-collapse supernovae over long-delay events such as neutron star mergers.

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“…Since the age of a low-mass red giant star is dominated by the life time of its main-sequence evolutionary phase, one can obtain good age estimate from stellar evolutionary tracks if the stellar mass is known accurately (Ness et al 2016;Martig et al 2016;Wu et al 2018). With this approach, Martig et al (2016) obtained ages for 1475 APOKASC stars (Pinsonneault et al 2014) that have mass estimates based on asteroseismology of the Kepler data.…”

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confidence: 99%

“…With this approach, Wu et al (2018) obtained precise ages of 6940 red giant branch (RGB) stars in the LAMOST-Kepler project (De Cat et al 2015, Ren et al 2016, Zong et al 2018, whose masses are determined with asteroseismic scaling relation using the seismic parameters of Yu et al (2018). Typical uncertainty of the mass estimates is a few per cent, and that of the age estimates is ∼ 20 per cent.…”

mentioning

confidence: 99%

“…Typical uncertainty of the mass estimates is a few per cent, and that of the age estimates is ∼ 20 per cent. Wu et al (2018) also investigated the feasibility of deducing age and mass directly from the LAMOST spectra with a machine learning method based on kernel based principal component analysis (KPCA) by taking the LAMOST-Kepler sample stars as a training data set, and show that the stellar age thus derived achieve a precision of ∼ 24 per cent.…”

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confidence: 99%

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Ages and masses of 0.64 million red giant branch stars from the LAMOST Galactic Spectroscopic Survey

Xiang

Zhao

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a catalog of stellar age and mass estimates for a sample of 640 986 red giant branch (RGB) stars of the Galactic disk from the LAMOST Galactic Spectroscopic Survey (DR4). The RGB stars are distinguished from the red clump stars utilizing period spacing derived from the spectra with a machine learning method based on kernel principal component analysis (KPCA). Cross-validation suggests our method is capable of distinguishing RC from RGB stars with only 2 per cent contamination rate for stars with signal-to-noise ratio (SNR) higher than 50. The age and mass of these RGB stars are determined from their LAMOST spectra with KPCA method by taking the LAMOST -Kepler giant stars having asteroseismic parameters and the LAMOST-TGAS sub-giant stars based on isochrones as training sets. Examinations suggest that the age and mass estimates of our RGB sample stars with SNR > 30 have a median error of 30 per cent and 10 per cent, respectively. Stellar ages are found to exhibit positive vertical and negative radial gradients across the disk, and the age structure of the disk is strongly flared across the whole disk of 6 < R < 13 kpc. The data set demonstrates good correlations among stellar age, [Fe/H] and [α/Fe]. There are two separate sequences in the [Fe/H] -[α/Fe] plane: a high-α sequence with stars older than ∼ 8 Gyr and a low-α sequence composed of stars with ages covering the whole range of possible ages of stars. We also examine relations between age and kinematic parameters derived from the Gaia DR2 parallax and proper motions. Both the median value and dispersion of the orbital eccentricity are found to increase with age. The vertical angular momentum is found to fairly smoothly decrease with age from 2 to 12 Gyr, with a rate of about −50 kpc km s −1 Gyr −1 . A full table of the catalog is public available online.

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Mass and age of red giant branch stars observed with LAMOST and Kepler

Cited by 50 publications

References 70 publications

Spatial variations in the Milky Way disc metallicity–age relation

Spatial variations in the Milky Way disc metallicity–age relation

The GALAH survey: temporal chemical enrichment of the galactic disc

Ages and masses of 0.64 million red giant branch stars from the LAMOST Galactic Spectroscopic Survey

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