J/A+A/708/A250 [C/N] and [Y/Mg] chemical clocks (Pakstiene+, 2026)
Calibration of the [C/N] and [Y/Mg] chemical clocks with asteroseismic ages
from the TESS space mission.
Pakstiene E., Tautvaisiene G., Bagdonas V., Kjeldsen H., Winther M.L.,
Drazdauskas A., Viscasillas Vazquez C., Chorniy Y., Mikolaitis S.,
Minkeviciute R., Stonkute E.
<Astron. Astrophys. 708, A250 (2026)>
=2026A&A...708A.250P 2026A&A...708A.250P (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Abundances ; Stars, ages ; Models
Keywords: stars: abundances - stellar evolution - Galaxy: disk
Abstract:
Stellar ages are typically very difficult to estimate for field stars.
New empirical methods, based on abundance ratios of chemical elements,
are emerging and need to be calibrated.
Our main aim is to contribute to revealing relations between [C/N] and
[Y/Mg] ratios and stellar ages by determining astroseismic ages,
non-local thermodynamic equilibrium abundances, and accounting for
stellar evolutionary stages and birth-places in the Galaxy.
We searched for solar-type pulsations in a sample of 1250 bright F, G,
and K giants using data from the TESS space telescope and determined
asteroseismic ages using BASTA and PARAM codes. For the [Y/Mg]
relations with age, we determined abundances accounting for deviations
from the local thermodynamic equilibrium. For the [C/N] relations with
age, we separated stars according to their evolutionary stages.
We determined asteroseismic ages for 218 giants and derived [Y/Mg] and
[C/N] relations with age for subsamples of stars in three regions of
the Galactic thin disc and the thick disc.
The [Y/Mg]-age relation exhibits a clear radial dependence across the
Galactic disc, with a steeper trend in the outer disc, progressively
flatter relations toward the inner disc, and very flat in the thick
disc. NLTE abundances of Mg and especially of Y have to be used to
have a more precise stellar age evaluation from [Y/Mg] ratios. When
using [C/N] abundance ratios as stellar age indicators, evolutionary
stages of stars have to be taken into account.
Description:
Solar-type pulsations were detected in a sample of 218 bright F, G,
and K giants using data from the TESS space telescope. Asteroseismic
ages and masses were determined using BASTA and PARAM codes.
Asteroseismic data were used to determine the evolutionary stages of
stars. Carnon, nitrogen, magnesium, and yttrium abundances were
determined using high-resolution spectra obtained with the 1.65m
telescope at the Moletai Astronomical Observatory. Mg and Y abundances
were corrected for the non-local thermodynamic equilibrium effects.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 167 218 Parameters of studied stars
--------------------------------------------------------------------------------
See also:
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- ID Tycho-2 catalogue identification (ID)
16- 20 F5.2 Gyr AgePARAM Asteroseismic age determined using
PARAM(v.1.5) (Age_PARAM)
22- 25 F4.2 Gyr e_AgePARAM Lower uncertainty (68% credible interval) in
the age determination with PARAM
(eloAge_PARAM)
27- 30 F4.2 Gyr E_AgePARAM Upper uncertainty (68% credible interval) in
the age determination with PARAM
(eupAge_PARAM)
32- 36 F5.2 Gyr AgeBASTA ? Asteroseismic age determined using BASTA
(Age_BASTA)
38- 41 F4.2 Gyr e_AgeBASTA ? Lower uncertainty (16th quantile) in the
age determination with BASTA
(eloAge_BASTA)
43- 46 F4.2 Gyr E_AgeBASTA ? Upper uncertainty (84th quantile) in the
age determination with BASTA
(eupAge_BASTA)
48- 52 F5.2 Gyr AgeAstero Asteroseismic age, averaged when both PARAM
and BASTA age values available
(Age_Asteroseismic)
54- 58 F5.1 uHz numax Frequency at maximum power (Numax)
60- 64 F5.2 uHz e_numax Uncertainty in frequency at maximum power
(e_Numax)
66- 70 F5.2 uHz Deltanu Large frequency separation (DeltaNu)
72- 75 F4.2 uHz e_Deltanu Uncertainty in large frequency separation
(e_DeltaNu)
77- 80 F4.2 Msun MassPARAM Stellar mass determined using PARAM(v.1.5)
(Mass_PARAM)
82- 85 F4.2 Msun e_MassPARAM Lower uncertainty (68% credible interval) of
mass determined with PARAM
(eloMass_PARAM)
87- 90 F4.2 Msun E_MassPARAM Upper uncertainty (68% credible interval) of
mass determined with PARAM
(eupMass_PARAM)
92- 95 F4.2 Msun MassBASTA ? Stellar mass determined with BASTA
(Mass_BASTA)
97-100 F4.2 Msun e_MassBASTA ? Lower uncertainty (16th quantile) of mass
determined with BASTA (eloMass_BASTA)
102-105 F4.2 Msun E_MassBASTA ? Upper uncertainty (84th quantile) of mass
determined with BASTA (eupMass_BASTA)
107-110 F4.2 Msun MassAstero ? Asteroseismic mass, averaged when both
PARAM and BASTA mass values available
(Mass_Asteroseismic)
112-116 F5.2 [-] [Mg/H]LTE ? LTE magnesium abundance from Paper I or
Paper III ([Mg/H]LTE)
118-122 F5.2 [-] [Mg/H]NLTE ? NLTE magnesium abundance ([Mg/H]NLTE)
124-128 F5.2 [-] [Y/H]LTE1 ? LTE yttrium abundance from Paper II
([Y/H]LTE_1)
130-134 F5.2 [-] [Y/H]LTE2 ? LTE yttrium abundance determined in this
work ([Y/H]LTE_2)
136-139 F4.2 [-] e_[Y/H]LTE2 ? Uncertainty in LTE yttrium abundance
determined in this work (e[Y/H]LTE2)
141-145 F5.2 [-] [Y/H]NLTE ? NLTE yttrium abundance ([Y/H]NLTE)
147-151 F5.2 [-] [C/N] ? Ratio of [C/N] from Paper I or Paper III
([C/N])
153-156 F4.2 --- C/N ? Carbon-to-nitrogen abundance ratio from
Paper I or Paper III (C/N)
158-163 A6 --- Evol Evolutionary stage (Evol) (1)
165 I1 --- EvolMethod [1/2]? Method of the evolutionary stage
determination (Evol_method) (2)
167 I1 --- Disc [0/1]? 0 = Thin disc, 1 = Thick disc;
taken from Paper I or Paper III (Disc)
--------------------------------------------------------------------------------
Note (1): Evolutionary stage as follows:
RGB BB = stars below the RGB luminosity bump
RGB AB = stars above the RGB luminosity bump
RC = clump stars
Note (2): Method of the evolutionary stage as follows:
1 = if determined purely from asteroseismic data
2 = if isochronal information was involved
--------------------------------------------------------------------------------
Acknowledgements:
From Vilius Bagdonas, vilius.bagdonas(at)ff.vu.lt
This paper includes data collected by the TESS mission. Funding for
the TESS mission is provided by the NASA's Science Mission
Directorate.
We acknowledge funding from the Research Council of Lithuania (LMTLT,
grant No. S-MIP-23-24).
(End) Patricia Vannier [CDS] 17-Feb-2026