The solar lithium abundance

Solar Physics ◽  
1975 ◽  
Vol 41 (1) ◽  
pp. 53-65 ◽  
Author(s):  
Edith A Müller ◽  
Eric Peytremann ◽  
Ramiro de la Reza
Keyword(s):  
1968 ◽  
Vol 1 ◽  
pp. 243-246
Author(s):  
Edith A. Müller

The determination of the lithium abundance in the solar atmosphere is essentially based on the LiI resonance doublet at λ 6707·761 and 6707·912 Å. These two lines form a very faint absorption feature, the central depth of the stronger component being of the order of 1% of the continuum. The violet component, which is also the stronger of the two, occurs near the red wing of a faint solar line of unknown origin, and the lines appear to be blended with other faint lines including possibly the doublet of the Li6 isotope (the isotopic shift being 0·160 Å). No other line of LiI has been detected in the Fraunhofer spectum of the undisturbed solar disk. This is nothing surprising, because practically all lithium is expected to be ionized in the photosphere on account of its low ionization potential (Xion = 5·37 e.v.). In sunspot spectra the lower temperature reduces the degree of ionization of lithium and causes a strengthening of the LiI lines. In fact, the LiI resonance lines which appear as a very faint absorption feature on disk spectra are about 50 times stronger in spot spectra. Furthermore, the very weak feature at λ 6103·6 Å was identified by Dubov (1964) and by Schmahl and Schröter (1965) as due to the 2s 2S–3d 2D transition of LiI. Both the resonance doublet and the faint feature at 6103·6 Å have been used by the above-mentioned authors to derive the lithium abundance in spots.


Author(s):  
N Holanda ◽  
N Drake ◽  
W J B Corradi ◽  
F A Ferreira ◽  
F Maia ◽  
...  

Abstract We present the results of a chemical analysis of fast and anomalous rotator giants members of the young open cluster NGC 6124. For this purpose, we carried out abundances of the mixing sensitive species such as Li, C, N, Na and 12C/13C isotopic ratio, as well as other chemical species for a sample of four giants among the seven observed ones. This study is based on standard spectral analysis technique using high-resolution spectroscopic data. We also performed an investigation of the rotational velocity (v sin  i) once this sample exhibit abnormal values – giant stars commonly present rotational velocities of few km s−1. In parallel, we have been performed a membership study, making use of the third data release from ESA Gaia mission. Based on these data, we estimated a distance of d = 630 pc and an age of 178 Myr through isochrone fitting. After that procedure, we matched all the information raised and investigated the evolutionary stages and thermohaline mixing model through of spectroscopic Teff and log  g and mixing tracers, as 12C/13C and Na, of the studied stars. We derived a low mean metallicity of [Fe/H] = −0.13 ±0.05 and a modest enhancement of the elements created by the s-process such as Y, Zr, La, Ce, and Nd, which is in agreement of what has already been reported in the literature for young clusters. The giants analyzed have homogeneous abundances, except for lithium abundance [log  ε(Li)NLTE = 1.08±0.42] and this may be associated to a combination of mechanisms that act increasing or decreasing lithium abundances in stellar atmospheres.


Author(s):  
Satoshi Honda ◽  
Yuta Notsu ◽  
Hiroyuki Maehara ◽  
Shota Notsu ◽  
Takuya Shibayama ◽  
...  
Keyword(s):  

2009 ◽  
Vol 5 (S268) ◽  
pp. 201-210
Author(s):  
Monique Spite ◽  
François Spite

AbstractThe nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li?


2018 ◽  
Vol 618 ◽  
pp. A134 ◽  
Author(s):  
A. Mucciarelli ◽  
M. Salaris ◽  
L. Monaco ◽  
P. Bonifacio ◽  
X. Fu ◽  
...  

We present Li, Na, Al, and Fe abundances of 199 lower red giant branch star members of the stellar system Omega Centauri, using high-resolution spectra acquired with FLAMES at the Very Large Telescope. The A(Li) distribution is peaked at A(Li) ∼ 1 dex with a prominent tail towards lower values. The peak of the distribution well agrees with the lithium abundances measured in lower red giant branch stars in globular clusters and Galactic field stars. Stars with A(Li) ∼ 1 dex are found at metallicities lower than [Fe/H] ∼ –1.3 dex but they disappear at higher metallicities. On the other hand, Li-poor stars are found at all metallicities. The most metal-poor stars exhibit a clear Li–Na anti-correlation, where about 30% of the sample have A(Li) lower than ∼0.8 dex, while these stars represent a small fraction of normal globular clusters. Most of the stars with [Fe/H] > –1.6 dex are Li poor and Na rich. The Li depletion measured in these stars is not observed in globular clusters with similar metallicities and we demonstrate that it is not caused by the proposed helium enhancements and/or young ages. Hence, these stars formed from a gas already depleted in lithium. Finally, we note that Omega Centauri includes all the populations (Li-normal/Na-normal, Li-normal/Na-rich, and Li-poor/Na-rich stars) observed, to a lesser extent, in mono-metallic GCs.


2000 ◽  
Vol 198 ◽  
pp. 279-286
Author(s):  
Sushma V. Mallik

Recent observations of cool giants have shown that there exists a large range in their lithium abundances even for apparently similar stars. In order to explore whether this large spread could be interpreted in terms of mass, the Li I line at 6707.8 Å has been observed in more than 100 stars and these data have been combined with the already known lithium abundance data in literature. Absolute magnitudes of these stars have been estimated from the Hipparcos data and an attempt has been made to understand the Li evolution of a star as a function of its mass and the evolutionary status. There are strong evidences for extra-mixing taking place on the red giant branch which explain the unusually low abundances observed.


2000 ◽  
Vol 198 ◽  
pp. 368-369
Author(s):  
L Pompéia ◽  
B Barbuy ◽  
M. Grenon

We have a list of nearby bulge-like turnoff stars with metallicities in the range −0.3 ≤ [Fe/H] ≤ +0.6, for which we have the absolute magnitude from Hipparcos, Geneva photometry (therefore temperature and metallicity), and radial velocity from Coravel (Grenon 1990, 1997). From Hipparcos data, the turnoff of these field stars indicate an age of 10-11 Gyr, which would be the age of the most metal-rich component of the bulge.We obtained high resolution échelle spectra with FEROS, with the aim to carry out detailed analysis of these stars. In this paper we present the Li abundance for 40 of these metal-rich and old dwarf stars, as a function of their temperatures.


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