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- ID:
- ivo://CDS.VizieR/J/A+A/614/A55
- Title:
- Lithium abundance in dwarfs & subgiants
- Short Name:
- J/A+A/614/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We address the existence and origin of the lithium (Li) desert, a region in the Li-Teff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the Teff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert).
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/81
- Title:
- Lithium abundance in M4 red giants
- Short Name:
- J/MNRAS/412/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Li and Fe abundances for 87 stars in the globular cluster M4, obtained by using high-resolution spectra collected with GIRAFFE at the Very Large Telescope. The targets range from the turn-off up to the red giant branch bump. The Li abundance in the turn-off stars is uniform, with an average value equal to A(Li)=2.30+/-0.02dex (sigma=0.10dex), consistent with the upper envelope of Li content measured in other globular clusters and in the halo field stars, confirming also for M4 the discrepancy with the primordial Li abundance predicted by Wilkinson Microwave Anisotropy Probe+ big bang nucleosynthesis (WMAP+BBNS).
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/4368
- Title:
- Lithium abundance of solar-like stars
- Short Name:
- J/MNRAS/451/4368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the determination of the lithium abundance [A(Li)] of 52 solar-like stars. For 41 objects the A(Li) here presented corresponds to the first measurement. We have measured the equivalent widths of the 6708 {AA} lithium feature in high-resolution spectroscopic images (R~80000), obtained at the Observatorio Astrofisico Guillermo Haro (Sonora, Mexico), as part of the first scientific observations of the revitalized Lunar and Planetary Laboratory (LPL) Echelle Spectrograph, now known as the Cananea High-resolution Spectrograph (CanHiS). Lithium abundances were derived with the Fortran code MOOG, using as fundamental input a set of atmospheric parameters recently obtained by our group. With the help of an additional small sample with previous A(Li) determinations, we demonstrate that our lithium abundances are in agreement, to within uncertainties, with other works. Two target objects stand out from the rest of the sample. The star BD+47 3218 (T_eff_=6050+/-52 K, A(Li)=1.86+/-0.07 dex) lies inside the so-called lithium desert in the A(Li)-T_eff_ plane. The other object, BD+28 4515, has an A(Li)=3.05+/-0.07 dex, which is the highest of our sample and compatible with the expected abundances of relatively young stars.
- ID:
- ivo://CDS.VizieR/J/A+A/371/943
- Title:
- Lithium abundances for 185 main-sequence stars
- Short Name:
- J/A+A/371/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table presents stellar atmospheric parameters, absolute magnitude, mass, age, equivalent width of the {lambda}6708 Li line, and non-LTE Li abundance. For the majority of stars the absolute magnitude has been derived from Hipparcos parallaxes but in a few cases (marked by :) a photometric value derived from the c_1_ index is given. Most stellar ages have errors of around 20% but those marked with `:' are more uncertain, and for stars close to the ZAMS no age is given.
- ID:
- ivo://CDS.VizieR/J/A+A/595/A18
- Title:
- Lithium abundances in AMBRE stars
- Short Name:
- J/A+A/595/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The goal of this paper is to investigate the lithium stellar content of Milky Way stars in order to put constraints on the lithium chemical enrichment in our Galaxy, in particular in both the thin and thick discs. We show that the interstellar lithium abundance increases with metallicity by 1dex from [M/H]=-1dex to +0.0dex. Moreover, we find that this lithium ISM abundance decreases by about 0.5dex at super-solar metallicity. Based on a chemical separation, we also observed that the stellar lithium content in the thick disc increases rather slightly with metallicity while the thin disc shows a steeper increase. The lithium abundance distribution of alpha-rich metal-rich stars has a peak at A(Li)~3 dex. We conclude that the thick disc stars suffered of a low lithium chemical enrichment, showing lithium abundances rather close to the Spite plateau while the thin disc stars clearly show an increasing lithium chemical enrichment with the metallicity, probably thanks to the contribution of low-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A151
- Title:
- Lithium abundances in 714 F and G dwarf stars
- Short Name:
- J/A+A/615/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed analysis of Li in 714 nearby dwarf stars. Li abundances were determined through spectral line synthesis of the Li feature at 670.8 nm. The stellar sample traces the evolution of the Galactic thin and thick disks in the solar neighbourhood, and is the same as previously analysed by Bensby et al. (2014, Cat. J/A+A/562/A71) where stellar parameters and ages were taken from. The same sample was also used in Battistini & Bensby (2015, Cat. J/A+A/577/A9, 2016, Cat. J/A+A/586/A49) wherein abundances for odd iron-peak elements and r- and s-process elements can be found.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/46
- Title:
- Lithium abundances in HIP stars
- Short Name:
- J/ApJ/756/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive atmospheric parameters and lithium abundances for 671 stars and include our measurements in a literature compilation of 1381 dwarf and subgiant stars. First, a "lithium desert" in the effective temperature (T_eff_) versus lithium abundance (A_Li_) plane is observed such that no stars with T_eff_=~6075K and A_Li_=~1.8 are found. We speculate that most of the stars on the low A_Li_ side of the desert have experienced a short-lived period of severe surface lithium destruction as main-sequence or subgiant stars. Next, we search for differences in the lithium content of thin-disk and thick-disk stars, but we find that internal processes have erased from the stellar photospheres their possibly different histories of lithium enrichment. Nevertheless, we note that the maximum lithium abundance of thick-disk stars is nearly constant from [Fe/H]=-1.0 to -0.1, at a value that is similar to that measured in very metal-poor halo stars (A_Li_=~2.2). Finally, differences in the lithium abundance distribution of known planet-host stars relative to otherwise ordinary stars appear when restricting the samples to narrow ranges of T_eff_ or mass, but they are fully explained by age and metallicity biases. We confirm the lack of a connection between low lithium abundance and planets. However, we find that no low A_Li_ planet-hosts are found in the desert T_eff_ window. Provided that subtle sample biases are not responsible for this observation, this suggests that the presence of gas giant planets inhibit the mechanism responsible for the lithium desert.
- ID:
- ivo://CDS.VizieR/J/A+A/372/862
- Title:
- Lithium abundances in IC 2602 and IC 2391
- Short Name:
- J/A+A/372/862
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lithium abundances and [Fe/H] for a sample of late-type stars in the young open clusters IC 2602 and IC 2391. Abundances are based on high resolution spectra obtained at ESO (3.6m + CASPEC) and CTIO (4m + echelle spectrograph)
- ID:
- ivo://CDS.VizieR/J/A+A/634/A130
- Title:
- Lithium abundances in microlensed bulge dwarfs
- Short Name:
- J/A+A/634/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the ^7^Li line at 6707{AA} in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds another piece of evidence for a tight connection between the metal-poor bulge and the Galactic thick disk. For the bulge stars younger than about eight billion years, the sample contains a group of stars at very high metallicities at [Fe/H]~=+0.4 that have lithium abundances in the range A(Li)=2.6-2.8. In the solar neighbourhood the lithium abundances have been found to peak at A(Li)~=3.3 at [Fe/H]~=+0.1 and then decrease by 0.4-0.5dex when reaching [Fe/H]~=+0.4. The few bulge stars that we have at these metallicities seem to support this declining A(Li) trend. This could indeed support the recent claim that the low A(Li) abundances at the highest metallicities seen in the solar neighbourhood could be due to stars from the inner disk, or the bulge region, that have migrated to the solar neighbourhood.