The <sup>6</sup>Li/<sup>7</sup>Li isotopic ratio in the metal-poor binary CS22876–032

Hernández, J. I. González; Bonifacio, P.; Caffau, E.; Ludwig, H.‐G.; Steffen, M.; Monaco, L.; Cayrel, Roger

doi:10.1051/0004-6361/201936011

Cited by 14 publications

(4 citation statements)

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“…In particular, the 3D NLTE approach is important to characterize the calibration lines, to decrease the observational error. Eventually, a very recent publication by González Hernández et al (2019), confirms the non detection of 6 Li for a very metal poor binary star [(Fe/H) ∼−3.7 dex], finding an upper limit for the isotopic ratio of 6 Li/ 7 Li < 10%.…”

Section: Uncertainties On Atmospheric Models For Surface Lithium Abundance Determinationmentioning

confidence: 84%

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Tognelli

Degl’Innocenti

Moroni

et al. 2021

Front. Astron. Space Sci.

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Theoretical prediction of surface stellar abundances of light elements–lithium, beryllium, and boron–represents one of the most interesting open problems in astrophysics. As well known, several measurements of 7Li abundances in stellar atmospheres point out a disagreement between predictions and observations in different stellar evolutionary phases, rising doubts about the capability of present stellar models to precisely reproduce stellar envelope characteristics. The problem takes different aspects in the various evolutionary phases; the present analysis is restricted to protostellar and pre-Main Sequence phases. Light elements are burned at relatively low temperatures (T from ≈2 to ≈5 million degrees) and thus in the early evolutionary stages of a star they are gradually destroyed at different depths of stellar interior mainly by (p, α) burning reactions, in dependence on the stellar mass. Their surface abundances are strongly influenced by the nuclear cross sections, as well as by the extension toward the stellar interior of the convective envelope and by the temperature at its bottom, which depend on the characteristics of the star (mass and chemical composition) as well as on the energy transport in the convective stellar envelope. In recent years, a great effort has been made to improve the precision of light element burning cross sections. However, theoretical predictions surface light element abundance are challenging because they are also influenced by the uncertainties in the input physics adopted in the calculations as well as the efficiency of several standard and non-standard physical processes active in young stars (i.e. diffusion, radiative levitation, magnetic fields, rotation). Moreover, it is still not completely clear how much the previous protostellar evolution affects the pre-Main Sequence characteristics and thus the light element depletion. This paper presents the state-of-the-art of theoretical predictions for protostars and pre-Main Sequence stars and their light element surface abundances, discussing the role of (p, α) nuclear reaction rates and other input physics on the stellar evolution and on the temporal evolution of the predicted surface abundances.

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Section: Uncertainties On Atmospheric Models For Surface Lithium Abundance Determinationmentioning

confidence: 84%

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Tognelli

Degl’Innocenti

Moroni

et al. 2021

Front. Astron. Space Sci.

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“…In addition, for 7 Li, primordial BBN production is also included. Top panel: the BBN/GCRN 7 Li/H abundance is contrasted with elemental Li/H abundance data compiled from [7, 39, 59, 94-97, 100, 193-202]; stars shown have T eff > 6000 K. Bottom panel: the GCRN 6 Li/H abundance contrasted with data (upper limits) compiled from [43,92,93,193]. can explain the evolution the BeB isotopes.…”

Section: Jcap10(2022)078mentioning

confidence: 99%

“…The data for 6 Li and 7 Li in figure 2 come from many sources. For 6 Li, we use data giving only upper limits from [43,92,93,193], and for 7 Li there has been a substantial amount of JCAP10(2022)078 new data 5 as discussed above [7, 39, 59, 94-97, 100, 193-202]. Because lithium destruction is known to be a sensitive function of effective temperature (which correlates with the depth of the convective zone), we follow the standard practice of only showing abundances for hot stars, with T eff > 6000 K.…”

Section: Jcap10(2022)078mentioning

confidence: 99%

Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem

Fields

Olive

2022

J. Cosmol. Astropart. Phys.

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The primordial Lithium Problem is intimately connected to the assumption that the 7Li abundance observed in metal-poor halo stars is unchanged from its primordial value, which lies significantly below the predictions of standard big-bang nucleosynthesis. Two key lines of evidence have argued that these stars have not significantly depleted their initial (mostly primordial) 7Li: i) the lack of dispersion in Li abundance measurements at low metallicity (and high surface temperature); and ii) the detection of the more fragile 6Li isotope in at least two halo stars. The purported 6Li detections were in good agreement with predictions from cosmic-ray nucleosynthesis which is responsible for the origin of 6Li. This concordance left little room for 6Li depletion, and the apparent 6Li survival implied that 7Li largely evaded destruction, because stellar interiors destroy 6Li more vigorously then than 7Li. Recent (re)-observations of halo stars challenge the evidence against 7Li depletion: i) lithium elemental abundances now show significant dispersion, and ii) sensitive 6Li searches now reveal only upper limits to the 6Li/7Li ratio. We discuss the consequences of these 6Li non-detections on the primordial 7Li Problem, Galactic cosmic-ray nucleosynthesis, and the question of differential depletion of Li in stars. The tight new 6Li upper limits generally fall far below the predictions of cosmic-ray nucleosynthesis, implying that substantial 6Li depletion has occurred — by factors up to 50. We show that in stars with 6Li limits and thus lower bounds on 6Li depletion, an equal amount of 7Li depletion is more than sufficient to resolve the primordial 7Li Problem. This picture is consistent with well-studied stellar models in which 7Li is less depleted than 6Li, and strengthen the case that the Lithium Problem has an astrophysical solution. We conclude by suggesting future observations that could test these ideas.

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“…Beyond this series of papers, studies of lithium in metal-poor stars have provided crucial mass- and metallicity-dependent constraints (González Hernández et al. 2009 , 2019; Meléndez et al. 2010 ; Nissen & Schuster 2012 ).…”

Section: Introductionmentioning

confidence: 99%

Atomic diffusion and mixing in old stars – VIII. Chemical abundance variations in the globular cluster M4 (NGC 6121)

Nordlander,

Gruyters,

Richard

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Variations in chemical abundances with evolutionary phase have been identified among stars in globular and open clusters with a wide range of metallicities. In the metal-poor clusters, these variations compare well with predictions from stellar structure and evolution models considering the internal diffusive motions of atoms and ions, collectively known as atomic diffusion, when moderated by an additional mixing process with a fine-tuned efficiency. We present here an investigation of these effects in the Galactic globular cluster NGC 6121 (M4) ([Fe/H] = −1.13) through a detailed chemical abundance analysis of 86 stars using high-resolution ESO/VLT FLAMES spectroscopy. The stars range from the main-sequence turnoff point (TOP) to the red giant branch (RGB) just above the bump. We identify C-N-O and Mg-Al-Si abundance anti-correlations, and confirm the presence of a bimodal population differing by 1 dex in nitrogen abundance. The composition of the second-generation stars imply pollution from both massive (20–40 $\rm M_{\odot}$) and asymptotic giant branch stars. We find evolutionary variations in chemical abundances between the TOP and RGB, which are robust to uncertainties in stellar parameters and modelling assumptions. The variations are weak, but match predictions well when employing efficient additional mixing. Without correcting for Galactic production of lithium, we derive an initial lithium abundance 2.63 ± 0.10, which is marginally lower than the predicted primordial BBN value.

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The ⁶Li/⁷Li isotopic ratio in the metal-poor binary CS22876–032

Cited by 14 publications

References 50 publications

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem

Atomic diffusion and mixing in old stars – VIII. Chemical abundance variations in the globular cluster M4 (NGC 6121)

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The 6Li/7Li isotopic ratio in the metal-poor binary CS22876–032

Cited by 14 publications

References 50 publications

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

Implications of the non-observation of 6Li in halo stars for the primordial 7Li problem

Atomic diffusion and mixing in old stars – VIII. Chemical abundance variations in the globular cluster M4 (NGC 6121)

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The ⁶Li/⁷Li isotopic ratio in the metal-poor binary CS22876–032

Implications of the non-observation of ⁶Li in halo stars for the primordial ⁷Li problem