J/A+A/655/A23 Open cluster red clump stars Lithium abundances (Magrini+, 2021)
Gaia-ESO survey: Lithium abundances in open cluster Red Clump stars.
Magrini L., Smiljanic R., Franciosini E., Pasquini L., Randich S.,
Casali G., Viscasillas Vazquez C., Bragaglia A., Spina L., Biazzo K.,
Tautvaisienne G., Masseron T., Van der Swaelmen M., Pancino E.,
Jimenez-Esteban F., Guiglion G., Martell S., Bensby T., D'Orazi V.,
Baratella M., Korn A., Jofre P., Gilmore G., Worley C., Hourihane A.,
Gonneau A., Sacco G.G., Morbidelli L.
<Astron. Astrophys. 655, A23 (2021)>
=2021A&A...655A..23M 2021A&A...655A..23M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, open ; Stars, giant ; Abundances
Keywords: stars: abundances - stars: evolution - stars: low-mass -
open clusters and associations: general
Abstract:
It has recently been suggested that all giant stars with masses below
2M☉ suffer an episode of surface lithium enrichment between the
tip of the red giant branch (RGB) and the red clump (RC). We test if
the above result can be confirmed in a sample of RC and RGB stars that
are members of open clusters.
We discuss Li abundances in six open clusters with ages between 1.5
and 4.9Gyr (turn-off masses between 1.1 and 1.7M☉). We compare
these observations with the predictions of different models that
include rotation-induced mixing, thermohaline instability, mixing
induced by the first He flash, and energy losses by neutrino magnetic
moment.
In six clusters, we find close to 35% of RC stars have Li abundances
that are similar or higher than those of upper RGB stars. This can be
a sign of fresh Li production. Because of the extra-mixing episode
connected to the luminosity bump, the expectation has been for RC
stars to have systematically lower surface Li abundances. However, we
cannot confirm that this possible Li production is ubiquitous. For
about 65% of RC giants, we can only determine upper limits in
abundances that could be hiding very low Li content.
Our results indicate the possibility that Li is being produced in the
RC, at levels that would not typically permit the classification of
these the stars as Li rich. The determination of their carbon isotopic
ratio would help to confirm that the RC giants have suffered extra
mixing followed by subsequent Li enrichment. The Li abundances of the
RC stars can be qualitatively explained by the models by using an
additional mixing episode close to the He flash.
Description:
For our analysis, we used a selection of member stars from the sample
of 57 open clusters with stellar parameters from Gaia- ESO idr6 and
analyzed in Magrini et al. (2021A&A...651A..84M 2021A&A...651A..84M, Cat. J/A+A/651/A84).
We defined two different samples: the first is composed of all cluster
members with 1M☉≤MMSTO≤1.8M☉ and a restricted range of
metallicity, namely: -0.2≤[Fe/H]≤+0.2dex, belonging to the clusters
Col261, Be39, NGC6791, M67, Haf10, Cz24, NGC2425, Trumpler20, NGC2141,
NGC2420, NGC2158, NGC2154
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 87 103 Red clump member stars of open clusters with
1M☉≤MMSTO≤1.8M☉ and -0.2≤[Fe/H]≤0.2
table3.dat 92 225 *RGB and RC member stars of the six open clusters
of Table 1
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Note on table3.dat: Clusters are Berkeley21, Berkeley32, NGC2141, NGC2158,
NGC2243 and Trumpler5.
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See also:
J/A+A/651/A84 : Li abundance and mixing in giant stars (Magrini+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- CName CName (HHMMSSss+DDMMSSs)
18- 27 A10 --- Cluster Cluster name
29- 34 F6.1 K Teff Effective temperature
36- 39 F4.1 K e_Teff Effective temperature error
41- 44 F4.2 [cm/s2] logg Surface gravity
46- 49 F4.2 [cm/s2] e_logg Surface gravity error
51- 55 F5.2 [-] [Fe/H] Metallicity
57- 60 F4.2 [-] e_[Fe/H] Metallicity error
62 I1 --- l_A(Li) [0/1] Limt flag on A(Li) (1 for upper limit)
64- 68 F5.2 [-] A(Li) Lithium abundance
70- 73 F4.2 [-] e_A(Li) ?=- Lithium abundance error
75- 78 F4.2 [Lsun] logLum ?=- Luminosity
80- 83 F4.2 [Lsun] e_logLum Luminosity error
85- 87 F3.1 Msun MSTO MSTO mass
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- CName CName (HHMMSSss+DDMMSSs)
18- 27 A10 --- Cluster Cluster name
29- 34 F6.1 K Teff Effective temperature
36- 39 F4.1 K e_Teff Effective temperature error
41- 44 F4.2 [cm/s2] logg Surface gravity
46- 49 F4.2 [cm/s2] e_logg Surface gravity error
51- 55 F5.2 [-] [Fe/H] Metallicity
57- 60 F4.2 [-] e_[Fe/H] Metallicity error
62 I1 --- l_A(Li) [0/1] Limt flag on A(Li) (1 for upper limit)
64- 68 F5.2 [-] A(Li) Lithium abundance
70- 73 F4.2 [-] e_A(Li) ?=- Lithium abundance error
75- 78 F4.2 [Lsun] logLum Luminosity
80- 83 F4.2 [Lsun] e_logLum Luminosity error
85- 87 F3.1 Msun MSTO MSTO mass
89- 92 A4 --- Phase Phase (RC, LRGB, or URGB) (1)
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Note (1): Phase as follows:
RC = red clump star
LRGB = lower RGB star
URGB = upper RGB star
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Acknowledgements:
Laura Magrini, laura.magrini(at)inaf.it
(End) Patricia Vannier [CDS] 29-Sep-2021