J/A+A/624/A78 Masses and ages of 1059 HARPS-GTO stars (Delgado Mena+, 2019)
Abundance to age ratios in the HARPS-GTO sample with Gaia DR2.
Chemical clocks for a range of [Fe/H].
Delgado Mena E., Moya A., Adibekyan V., Tsantaki M.,
Gonzalez Hernandez J.I., Israelian G., Davies G.R., Chaplin W.J.,
Sousa S.G., Ferreira A., Santos N.C.
<Astron. Astrophys. 624, A78 (2019)>
=2019A&A...624A..78D 2019A&A...624A..78D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Stars, double and multiple ;
Stars, masses ; Stars, ages ; Parallaxes, trigonometric
Keywords: stars: abundances - stars: fundamental parameters -
Galaxy: evolution - Galaxy: disk - solar neighborhood
Abstract:
The purpose of this work is to evaluate how several elements produced
by different nucleosynthesis processes behave with stellar age and
provide empirical relations to derive stellar ages from chemical
abundances.
We derived different sets of ages using Padova and Yonsei-Yale
isochrones and Hipparcos and Gaia parallaxes for a sample of more than
1000 FGK dwarf stars for which he have high-resolution R∼115000 and
high-quality spectra from the HARPS-GTO program. We analyzed the
temporal evolution of different abundance ratios to find the best
chemical clocks. We applied multivariable linear regressions to our
sample of stars with a small uncertainty on age to obtain empirical
relations of age as a function of stellar parameters and different
chemical clocks.
We find that [alpha/Fe] ratio (average of Mg, Si, and Ti), [O/Fe] and
[Zn/Fe] are good age proxies with a lower dispersion than the
age-metallicity dispersion. Several abundance ratios present a
significant correlation with age for chemically separated thin disk
stars (i.e., low-alpha) but in the case of the chemically defined
thick disk stars (i.e., high-alpha) only the elements Mg, Si, Ca, and
TiII show a clear correlation with age. We find that the thick disk
stars are more enriched in light-s elements than thin disk stars of
similar age. The maximum enrichment of s-process elements in the thin
disk occurs in the youngest stars which in turn have solar
metallicity. The slopes of the [X/Fe]-age relations are quite constant
for O, Mg, Si, Ti, Zn, Sr, and Eu regardless of the metallicity.
However, this is not the case for Al, Ca, Cu and most of the s-process
elements, which display very different trends depending on the
metallicity. This demonstrates the limitations of using simple linear
relations based on certain abundance ratios to obtain ages for stars
of different metallicities. Finally, we show that by using 3D
relations with a chemical clock and two stellar parameters (either
Teff, [Fe/H] or stellar mass) we can explain up to 89% of age
variance in a star. A similar result is obtained when using 2D
relations with a chemical clock and one stellar parameter, explaining
up to a 87% of the variance.
The complete understanding of how the chemical elements were produced
and evolved in the Galaxy requires the knowledge of stellar ages and
precise chemical abundances. We show how the temporal evolution of
some chemical species change with metallicity, with remarkable
variations at super-solar metallicities, which will help to better
constrain the yields of different nucleosynthesis processes along the
history of the Galaxy.
Description:
The baseline sample used in this work consist of 1111 FGK stars
observed within the context of the HARPS-GTO planet search programs
(Mayor et al., 2003Msngr.114...20M 2003Msngr.114...20M; Lo Curto et al., 2010, Cat.
J/A+A/512/A48; Santos et al., 2011, Cat. J/A+A/526/A112). The final
spectra have a resolution of R∼115000 and high signal-to-noise ratio
(45% of the spectra have 100<S/N<300, 40% of the spectra have S/N>300
and the mean S/N is 380). Precise stellar parameters for the full
sample of 1111 stars within the HARPS-GTO program were homogeneously
derived in Sousa et al. (2008, Cat. J/A+A/487/373, 2011a,
Cat.J/A+A/526/A99, 2011b, Cat. J/A+A/533/A141). The parameters for
cool stars were revised by Tsantaki et al. (2013, Cat. J/A+A/555/A150)
using a special list of iron lines which was later applied to the full
sample in Delgado Mena et al. (2017, Cat. J/A+A/606/A94), also
correcting the spectroscopic gravities. From the 1111 stars in the
original sample, the derivation of parameters converged to a solution
for 1059 of them.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 55 1059 Stellar masses and ages
--------------------------------------------------------------------------------
See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/487/373 : Spectroscopic parameters of 451 HARPS-GTO stars (Sousa+, 2008)
J/A+A/512/A48 : HD125612, HD215497, HIP5158 HARPS RV curves (Lo Curto+, 2010)
J/A+A/526/A99 : Metal-poor solar-type stars spectroscopy & masses
(Sousa+, 2011)
J/A+A/526/A112 : Radial velocities of HARPS metal-poor sample (Santos+, 2011)
J/A+A/533/A141 : Stellar parameters for 582 HARPS FGK stars (Sousa+, 2011)
J/A+A/555/A150 : Physical parameters of cool solar-type stars (Tsantaki+, 2013)
J/A+A/606/A94 : Chemical abundances of 1059 FGK stars (Delgado Mena+, 2017)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Star Star's identifier
12- 16 F5.3 Msun Mass ?=- Stellar Mass
18- 22 F5.3 Msun e_Mass ?=- Error of Stellar Mass
24- 29 F6.3 Gyr Age ?=- Stellar Age
31- 35 F5.3 Gyr e_Age ?=- Error of Stellar Age
37- 41 F5.2 mag Vmag V magnitude
43- 49 F7.3 mas Plx Gaia DR2 Parallax
51- 55 F5.3 mas e_Plx error of parallax
--------------------------------------------------------------------------------
Acknowledgements:
Elisa Delgado Mena, elisa.delgado(at)astro.up.pt
(End) Elisa Delgado Mena [IA, Portugal], Patricia Vannier [CDS] 02-Apr-2019