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Benchmark ages for the Gaia benchmark stars

Sahlholdt, Christian L. LU ; Feltzing, Sofia LU ; Lindegren, Lennart LU and Church, Ross P. LU (2019) In Monthly Notices of the Royal Astronomical Society 482(1). p.895-920
Abstract

In the era of large-scale surveys of stars in the MilkyWay, stellar ages are crucial for studying the evolution of the Galaxy.But determining ages of field stars is notoriously difficult; therefore, we attempt to determine benchmark ages for the extensively studied Gaia benchmark stars which can be used for validation purposes. By searching the literature for age estimates from different methods and deriving new ages based on Bayesian isochrone fitting, we are able to put reliable limits on the ages of 16 out of the 33 benchmark stars. The giants with well-defined ages are all young, and an expansion of the sample to include older giants with asteroseismic ages would be beneficial. Some of the stars have surface parameters inconsistent... (More)

In the era of large-scale surveys of stars in the MilkyWay, stellar ages are crucial for studying the evolution of the Galaxy.But determining ages of field stars is notoriously difficult; therefore, we attempt to determine benchmark ages for the extensively studied Gaia benchmark stars which can be used for validation purposes. By searching the literature for age estimates from different methods and deriving new ages based on Bayesian isochrone fitting, we are able to put reliable limits on the ages of 16 out of the 33 benchmark stars. The giants with well-defined ages are all young, and an expansion of the sample to include older giants with asteroseismic ages would be beneficial. Some of the stars have surface parameters inconsistent with isochrones younger than 16 Gyr. Including a-enhancement in the models when relevant resolves some of these cases, but others clearly highlight discrepancies between the models and observations. We test the impact of atomic diffusion on the age estimates by fitting to the actual surface metallicity of the models instead of the initial value and find that the effect is negligible except for a single turn-off star. Finally, we show that our ability to determine isochrone-based ages for large spectroscopic surveys largely mirrors our ability to determine ages for these benchmark stars, except for stars with log g ≳ 4.4 dex since their location in the Hertzsprung-Russell diagram is almost age insensitive. Hence, isochrone fitting does not constrain their ages given the typical uncertainties of spectroscopic stellar parameters.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Stars: fundamental parameters, Stars: late-type
in
Monthly Notices of the Royal Astronomical Society
volume
482
issue
1
pages
26 pages
publisher
Oxford University Press (OUP)
external identifiers
  • scopus:85057177298
ISSN
0035-8711
DOI
10.1093/mnras/sty2732
language
English
LU publication?
yes
id
3eacffce-2de1-40c9-947a-da583309300b
date added to LUP
2018-12-03 09:36:56
date last changed
2019-03-19 04:03:10
@article{3eacffce-2de1-40c9-947a-da583309300b,
  abstract     = {<p>In the era of large-scale surveys of stars in the MilkyWay, stellar ages are crucial for studying the evolution of the Galaxy.But determining ages of field stars is notoriously difficult; therefore, we attempt to determine benchmark ages for the extensively studied Gaia benchmark stars which can be used for validation purposes. By searching the literature for age estimates from different methods and deriving new ages based on Bayesian isochrone fitting, we are able to put reliable limits on the ages of 16 out of the 33 benchmark stars. The giants with well-defined ages are all young, and an expansion of the sample to include older giants with asteroseismic ages would be beneficial. Some of the stars have surface parameters inconsistent with isochrones younger than 16 Gyr. Including a-enhancement in the models when relevant resolves some of these cases, but others clearly highlight discrepancies between the models and observations. We test the impact of atomic diffusion on the age estimates by fitting to the actual surface metallicity of the models instead of the initial value and find that the effect is negligible except for a single turn-off star. Finally, we show that our ability to determine isochrone-based ages for large spectroscopic surveys largely mirrors our ability to determine ages for these benchmark stars, except for stars with log g ≳ 4.4 dex since their location in the Hertzsprung-Russell diagram is almost age insensitive. Hence, isochrone fitting does not constrain their ages given the typical uncertainties of spectroscopic stellar parameters.</p>},
  author       = {Sahlholdt, Christian L. and Feltzing, Sofia and Lindegren, Lennart and Church, Ross P.},
  issn         = {0035-8711},
  keyword      = {Stars: fundamental parameters,Stars: late-type},
  language     = {eng},
  number       = {1},
  pages        = {895--920},
  publisher    = {Oxford University Press (OUP)},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Benchmark ages for the Gaia benchmark stars},
  url          = {http://dx.doi.org/10.1093/mnras/sty2732},
  volume       = {482},
  year         = {2019},
}