2024AJ....168..103A -
Astron. J., 168, 103 (2024/September-0)
Li Evolution among Stars of Low/Intermediate Mass: the Metal-deficient Open Cluster NGC 2204.
ANTHONY-TWAROG B.J., DELIYANNIS C.P., STEINHAUER A., SUN Q. and TWAROG B.A.
Abstract (from CDS):
We have analyzed high-dispersion spectra in the Li 6708 Å region for 167 stars within the anticenter cluster NGC 2204. From 105 probable members, abundance analysis of 45 evolved stars produces [Fe/H] = -0.40 ± 0.12, [Si/Fe] = 0.14 ± 0.12, [Ca/Fe] = 0.29 ± 0.07, and [Ni/Fe] = -0.12 ± 0.10, where quoted errors are standard deviations. With E(B - V) = 0.07 and (m - M)0 = 13.12, appropriate isochrones provide an excellent match from the main sequence through the tip of the giant branch for an age of 1.85 ± 0.05 Gyr. Li spectrum synthesis produces A(Li) below 1.4 at the base of the red giant branch to a detectable value of -0.4 at the tip. Six probable asymptotic giant branch stars and all but one red clump star have only Li upper limits. A rapidly rotating red giant is identified as a possible Li-rich giant, assuming it is a red clump star. Main-sequence turnoff stars have a well-defined A(Li) = 2.83 ± 0.03 (sem) down to the Li-dip wall at the predicted mass of 1.29 M☉. Despite having the same isochronal age as the more metal-rich NGC 2506, the luminosity distribution of red giants reflects a younger morphology similar to NGC 7789, possibly indicating a deeper impact of metallicity on stellar structure and A(Li) than previously assumed. As in NGC 2506 and NGC 7789, the NGC 2204 turnoff exhibits a broad range of rotation speeds, making abundance estimation impossible for some stars. The place of the cluster within Galactic A(Li) evolution is discussed.
Abstract Copyright:
© 2024. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Open star clusters - Stellar abundances
VizieR on-line data:
<Available at CDS (J/AJ/168/103): table1.dat table4.dat table5.dat>
Status at CDS
:
Examining the need for a new acronym. // All or part of tables of objects will be ingested in SIMBAD with priority 1.
Simbad objects:
27
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