J/A+A/690/A323 RGB stars from the APO-K2 catalogue (Valle+, 2024)
Stellar model tests and age determination for RGB stars from the
APO-K2 catalogue.
Valle G., Dell'Omodarme M., Prada Moroni P.G., Degl'Innocenti S.
<Astron. Astrophys. 690, A323 (2024)>
=2024A&A...690A.323V 2024A&A...690A.323V (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Stars, giant ; Stars, masses ; Stars, ages ;
Stars, diameters
Keywords: methods: statistical - stars: evolution -
stars: fundamental parameters - stars: interiors - Galaxy: abundances
Abstract:
By adopting the recently empirically derived dependence of
α-elements on [alpha/Fe] instead of the conventionally applied
uniform one, we tested the agreement between stellar model predictions
and observations for RGB stars in the APO-K2 catalogue. We
particularly focused on the biases in effective temperature scales and
on the robustness of age estimations.
A slight {DELTA}T difference of 25K was detected between stars with
high and low α-enhancement. A multivariate analysis reveals a
dependence of {DELTA}T on both [Fe/H] and [α/Fe], and highlights
a significant dependence on stellar mass.
Despite differences in assumed chemical composition, our analysis,
through a fortunate cancellation effect, yields ages that are largely
consistent with recent studies of the same sample. Notably, our
analysis identifies a 6% fraction of stars younger than 4 Ga within
the high-α population. However, our analysis of the [C/N] ratio
supports the possible origin of the these stars as a result of mergers
or mass transfer events.
Description:
Leveraging the recently released APO-K2 catalogue (Schonhut-Stasik et
al. 2024AJ....167...50S 2024AJ....167...50S, Cat. J/AJ/167/50), we performed an
investigation of the agreement between stellar model predictions and
observations for RGB stars. To this purpose, we adopted the element
scaling with [α/Fe] as resulting from the analysis of Valle et
al. (2024, arXiv:2407.05960). The most notable correction is a trend
between oxygen and [α/Fe] that is steeper than assumed in a
uniform enhancement scenario.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 83 4246 Grid-based estimates of age, mass, and radius
for the selected RGB stars
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/AJ/167/50 : The APO-K2 Catalog. I. 7672 Red giants (Schonhut-Stasik+, 2024)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2- 20 A19 -- 2MASS 2MASS name (2MHHMMSSss+DDMMSSS)
22- 27 F6.2 Gyr Age Age
29- 34 F6.2 Gyr e_Age Age lower error
36- 41 F6.2 Gyr E_Age Age upper error
43- 48 F6.2 Msun Mass Mass
50- 55 F6.2 Msun e_Mass Mass lower error
57- 62 F6.2 Msun E_Mass Mass upper error
64- 69 F6.2 Rsun Rad Radius
71- 76 F6.2 Rsun e_Rad Radius lower error
78- 83 F6.2 Rsun E_Rad Radius upper error
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Acknowledgements:
Gaida Valle, giada.valle(at)df.unipi.it
(End) Gaida Valle [[University of Pisa], Patricia Vannier [CDS] 26-Aug-2024