Li isotopes in metal-poor halo dwarfs: a more and more complicated story

Spite, M.; Spite, F.

doi:10.1017/s1743921310004138

Cited by 5 publications

(7 citation statements)

References 32 publications

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“…At present, there exists a discrepancy between the predicted abundance of lithium-7 based on the WMAP results [107,102] for η, 7 Li/H = (5.14 ± 0.50) × 10 −10 and its values measured in metal-poor halo stars in our Galaxy [61], 7 Li/H = (1.26 ± 0.26) × 10 −10 which is factor 3 lower, at least [115] (see also Ref. [465]), than the predicted value. No solution to this Lithium-7 problem is known.…”

Section: Overviewmentioning

confidence: 80%

Varying Constants, Gravitation and Cosmology

Uzan

2011

Living Rev. Relativ.

752

784

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Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.

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Section: Overviewmentioning

confidence: 80%

Varying Constants, Gravitation and Cosmology

Uzan

2011

Living Rev. Relativ.

752

784

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“…Cayrel et al (2007) argued that asymmetric convective motions in stellar atmospheres could alter the profile of the Li line, mimicking the presence of 6 Li. Because of those uncertainties, the reality of high 6 Li values in halo stars has not been definitely established yet; the answer will require 3D model atmospheres in the non-LTE regime (see Asplund & Lind 201;Steffen et al 2010;and Spite & Spite 2010; and references therein). As clearly stated in Asplund & Lind (2010); "it is not yet possible to say that 6 Li has definitely been detected, but it is definitely too early to say that 6 Li has not been detected".…”

Section: Earlymentioning

confidence: 99%

“…Furthermore, observations of Li isotopic ratios became available, both in low-metallicity halo stars (Asplund et al 2006;Garcia-Perez et al 2009) and in the local ISM (Kawanomoto et al 2009). The former, suggesting a surprisingly high 6 Li/ 7 Li ratio in the early Galaxy, stimulated a large body of theoretical work (see Prantzos 2006b, and references therein) but remains controversial (Spite & Spite 2010, and references therein); the latter, combined to the well-known meteoritic ratio of 6 Li/ 7 Li, constrains the late evolution of Li isotopes in the local region of the Galaxy.…”

Section: Introductionmentioning

confidence: 99%

Production and evolution of Li, Be, and B isotopes in the Galaxy

Prantzos

2012

A&A

169

159

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Context. We reassess the problem of the production and evolution of the light elements Li, Be and B and of their isotopes in the Milky Way in the light of new observational and theoretical developments. Aims. The main novelty is the introduction of a new scheme for the origin of Galactic cosmic rays (GCR), which for the first time enables a self-consistent calculation of their composition during galactic evolution. Methods. The scheme accounts for key features of the present-day GCR source composition, it is based on the wind yields of the Geneva models of rotating, mass-losing stars and it is fully coupled to a detailed galactic chemical evolution code. Results. We find that the adopted GCR source composition accounts naturally for the observations of primary Be and helps understanding why Be follows Fe more closely than O. We find that GCR produce ∼70% of the solar 11 B/ 10 B isotopic ratio; the remaining 30% of 11 B presumably result from ν-nucleosynthesis in massive star explosions. We find that GCR and primordial nucleosynthesis can produce at most ∼30% of solar Li. At least half of the solar Li has to originate in low-mass stellar sources (red giants, asymptotic giant branch stars, or novae), but the required average yields of those sources are found to be much higher than obtained in current models of stellar nucleosynthesis. We also present radial profiles of LiBeB elemental and isotopic abundances in the Milky Way disc. We argue that the shape of those profiles -and the late evolution of LiBeB in general -reveals important features of the production of those light elements through primary and secondary processes.

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“…Asplund et al [12]) and it is below the detection level also for most thick disk and halo stars (see e.g. Spite and Spite [184]). The possible abundance of 6 Li below the limit of detection also for halo stars could be explained by the fact that the amount of 6 Li formed by the standard Big Bang and by the cosmic rays is supposed to be very low.…”

Section: Light Elements Surface Abundances and Nuclear Burning During...mentioning

confidence: 94%

Theoretical predictions of surface light element abundances in protostellar and pre-Main Sequence phase

Tognelli,

Degl'Innocenti,

Moroni

et al. 2021

Preprint

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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 7 Li 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 1 Tognelli et al.Light element abundances in protostellar and pre-main sequence phase. 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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Li isotopes in metal-poor halo dwarfs: a more and more complicated story

Cited by 5 publications

References 32 publications

Varying Constants, Gravitation and Cosmology

Varying Constants, Gravitation and Cosmology

Production and evolution of Li, Be, and B isotopes in the Galaxy

Theoretical predictions of surface light element abundances in protostellar and pre-Main Sequence phase

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