J/A+A/668/A126 Li-rich produced by element diffusion (Gao+, 2022)
Li-rich and super Li-rich giants produced by element diffusion.
Gao J., Zhu C., Yu J., Liu H., Lu X., Shi J., Lu G.
<Astron. Astrophys. 668, A126 (2022)>
=2022A&A...668A.126G 2022A&A...668A.126G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Abundances ; Effective temperatures ; Optical
Keywords: stars: abundances - stars: evolution - stars: low-mass - diffusion -
standards - gravitation
Abstract:
About 0.2-2% of giant stars are Li-rich, whose lithium abundance
(A(Li) is higher than 1.5dex. Among them, near 6% are super Li-rich
with A(Li) exceeding 3.2dex. Meanwhile, the formation mechanism of
these Li-rich and super Li-rich giants is still under debate.
Considering the compact He core of red giants, attention is paid to
the effect of element diffusion on A(Li). In particular, when the He
core flash occurs, the element diffusion makes the thermohaline mixing
zone extend inward and connect to the inner convection region of
stars. Then, a large amount of 7Be produced by the He flash can be
transferred to stellar surface, finally turning into 7Li. Thus, the
goal of this work is to propose the mechanism of A(Li) enrichment and
achieve the consistency between the theoretical and observation data.
In our model, the element diffusion mainly triggered by the gravity
field changes the mean molecular weight at the junction zone between
the stellar envelope and the He core, which makes the thermohaline
mixing region expanding to the inner convection region of stars. A
transport channel, efficiently transporting 7Be in the hydrogen
burning region of the star to the convective envelope where 7Be
decays into 7Li, is formed. Combing a high constant diffusive
mixing coefficients, the transport channel can explain the origin of
Li-rich and super Li-rich giant, even the most super Li-rich giants.
Description:
In recent years, many large survey programs have revealed the
existence of numerous Li-rich giants. In order to compare with the
theoretical results with observation samples in this work, we selected
351 published Li-rich giants with precise values of luminosity,
temperature and Li abundance as our samples. From about 11000
observational samples, the 351 Li-rich giant stars (Kuma et al.,
2011ApJ...730L..12K 2011ApJ...730L..12K; Yan et al., 2018NatAs...2..790Y 2018NatAs...2..790Y; Deepak & Reddyi,
2019MNRAS.484.2000D 2019MNRAS.484.2000D, Cat. J/MNRAS/484/2000) whose luminosities are
measured are selected in this work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 351 *Stellar parameters of Li-rich giants with Li
abundance in previous work
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Note on table1.dat: Kuma et al., 2011ApJ...730L..12K 2011ApJ...730L..12K;
Yan et al., 2018NatAs...2..790Y 2018NatAs...2..790Y;
Deepak & Reddyi, 2019MNRAS.484.2000D 2019MNRAS.484.2000D, Cat. J/MNRAS/484/2000
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See also:
J/MNRAS/478/4513 : GALAH Survey DR2 (Buder+, 2018)
J/MNRAS/484/2000 : Study of Lithium-rich giants with GALAH (Deepak+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 28 A28 --- ID Object ID
30- 36 F7.2 K Teff Effective temperature (1)
38- 41 F4.2 [cm/s2] logg Surface gravity (1)
43- 46 F4.2 --- A(Li) Lithium abundance
48- 51 F4.2 [Lsun] logL Star luminosity (2)
53- 57 F5.2 [-] [Fe/H] Iron to hydrogen abundance ratio
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Note (1): Values of effective temperature and logarithmic surface gravity are
adopted from the GALAH catalogue (Buder et al. 2018MNRAS.478.4513B 2018MNRAS.478.4513B,
Cat. J/MNRAS/478/4513)
Note (2): The values of luminosities are based on parallaxes and apparent
magnitudes taken from the Gaia catalogue
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Acknowledgements:
Jun Gao, jungao0929(at)163.com
(End) Patricia Vannier [CDS] 26-Oct-2022