Atomic diffusion in metal-poor stars

Salaris, Maurizio; Weiß, Achim

doi:10.1051/0004-6361:20010982

Cited by 137 publications

(308 citation statements)

References 29 publications

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“…This comparison is good when 2 H/H is considered, fair when 4 He, and inconclusive when 3 He is considered, but factor 2 − 3 discrepant in the case of 7 Li. It is not clear if this latter discrepancy is due to stellar 7 Li destruction effects, either in Pop II [3,4,5,6] stars where it is observed, or in a prior Pop III generation [7], or indeed due to a required modification of BBN, such as a population of decaying relics [8,9]. This discrepancy, however, is not subject of the present paper.…”

Section: Introductionmentioning

confidence: 76%

Big bang nucleosynthesis constraints on hadronically and electromagnetically decaying relic neutral particles

2006

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Big Bang nucleosynthesis in the presence of decaying relic neutral particles is examined in detail. All non-thermal processes important for the determination of light-element abundance yields of 2 H, 3 H, 3 He, 4 He, 6 Li, and 7 Li are coupled to the thermonuclear fusion reactions to obtain comparatively accurate results. Predicted light-element yields are compared to observationally inferred limits on primordial light-element abundances to infer constraints on the abundances and properties of relic decaying particles with decay times in the interval 0.01 sec < ∼ τX < ∼ 10 12 sec. Decaying particles are typically constrained at early times by 4 He or 2 H, at intermediate times by 6 Li, and at large times by the 3 He/ 2 H ratio. Constraints are shown for a large number of hadronic branching ratios and decaying particle masses and may be applied to constrain the evolution of the early Universe.

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Section: Introductionmentioning

confidence: 76%

Big bang nucleosynthesis constraints on hadronically and electromagnetically decaying relic neutral particles

2006

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“…Theoretical investigations of heavy-element diffusion in metal-poor stars by Michaud, Fontaine, & Beaudet (1984), Castellani et al (1997), Salaris, Groenwegen, & Weiss (2000), Weiss (2001), andChaboyer et al (2001), among others, suggest that it should be important in metal-poor stars at the main-sequence turnoff, while at the level of the RGB, the presence of deep surface convection zones should inhibit such processes. Such processes should manifest themselves most clearly in globular cluster stars because of their old age, giving lots of time for such phenomena to develop, and presumed identical initial chemical composition.…”

Section: No 1 2003mentioning

confidence: 99%

Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

Ramírez

Cohen

2003

The Astronomical Journal

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We present the iron abundance and abundance ratios for 18 elements with respect to Fe in a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in the globular cluster M5. The analyzed spectra, obtained with the High Resolution Echelle Spectrograph at the Keck Observatory, are of high dispersion (R = /D = 35,000). We find that the neutron capture, the iron peak, and the -element abundance ratios show no trend with T eff and low scatter around the mean between the top of the red giant branch and near the main-sequence turnoff, suggesting that at this metallicity non-LTE effects are not important over the range of stellar parameters spanned by our sample. To within the precision of the measurements (about AE0.1 dex), gravitationally induced heavy-element diffusion does not appear to be present among the stars near the main-sequence turnoff studied here. Our work and other recent studies suggest that heavy-element diffusion is inhibited in the surface layers of metal-poor stars. Differences in the Na abundance from star to star that extend to the main-sequence turnoff are detected in our sample in M5. The anticorrelation between O and Na abundances, observed in other metal-poor globular clusters, is not detected in our sample, but it may be hidden among stars with only upper limits for their O abundances. As we found in M71, there is a hint of star-to-star variation in the Zr abundance. Overall the abundance ratios of M5 appear very similar to those of M71, with the possible exception of the neutron capture element Ba, for which we argue that the apparent difference may be due to difficulties in the analysis. As in M71, the -elements Mg, Ca, Si, and Ti are overabundant relative to Fe. The results of our abundance analysis of 25 stars in M5 provide further evidence of abundance variations among specific light elements at unexpectedly low luminosities, which cannot be explained by our current understanding of stellar evolution.

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“…19 −0.13 . It should be kept in mind that there could be factor-oftwo effects associated with Li destruction in the observed stars [46,47,48] and with the stellar atmosphere models used to derive abundances [49]. There are two curves for 7 Li/H, reflecting the two paths for its production in BBN: a low-Ω B case in which 7 Li is produced directly, and a high-Ω B case in which 7 Li is produced as 7 Be, followed by beta decay.…”

Section: Observational Constraintsmentioning

confidence: 99%

Primordial nucleosynthesis with a varying fine structure constant: An improved estimate

Nollett

Lopez

2002

Phys. Rev. D

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We compute primordial light-element abundances for cases with fine structure constant α different from the present value, including many sources of α dependence neglected in previous calculations. Specifically, we consider contributions arising from Coulomb barrier penetration, photon coupling to nuclear currents, and the electromagnetic components of nuclear masses. We find the primordial abundances to depend more weakly on α than previously estimated, by up to a factor of 2 in the case of 7 Li. We discuss the constraints on variations in α from the individual abundance measurements and the uncertainties affecting these constraints. While the present best measurements of primordial D/H, 4 He/H, and 7 Li/H may be reconciled pairwise by adjusting α and the universal baryon density, no value of α allows all three to be accommodated simultaneously without consideration of systematic error. The combination of measured abundances with observations of acoustic peaks in the cosmic microwave background favors no change in α within the uncertainties.PACS numbers: 26.35.+c,98.80Ft,98.80.Es

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Atomic diffusion in metal-poor stars

Cited by 137 publications

References 29 publications

Big bang nucleosynthesis constraints on hadronically and electromagnetically decaying relic neutral particles

Big bang nucleosynthesis constraints on hadronically and electromagnetically decaying relic neutral particles

Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

Primordial nucleosynthesis with a varying fine structure constant: An improved estimate

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