Hyperfine-structure measurements of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Eu</mml:mi></mml:mrow><mml:mrow /><mml:mrow><mml:mo>+</mml:mo></mml:mrow><mml:mrow /><mml:mrow /><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mn>5</mml:mn><mml:mn>1</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn><mml:mn>5</mml:mn><mml:mn>3</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow>

Becker, O.; Enders, K.; Werth, G.; Dembczyński, J.

doi:10.1103/physreva.48.3546

Cited by 46 publications

(46 citation statements)

References 17 publications

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“…The synthetic spectra were produced using KURUCZ06 model atmospheres in conjunction with the 1D LTE code ATLAS, and the Eu line lists were constructed using hyperfine splitting information from Krebs & Winkler (1960) and Becker et al (1993). In addition, the isotopic ratio 0.5:0.5 for Eu 151:153 was adopted.…”

Section: Comparison With Previous Resultsmentioning

confidence: 99%

Origin of the heavy elements in HD 140283

Mello¹,

Barbuy²,

Spite³

et al. 2012

A&A

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Context. HD 140283 is a nearby (V = 7.7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 Å and 4205 Å, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 Å. Results. We were able to determine the abundance A(Eu) = −2.35 ± 0.07 dex, compatible with the value predicted for the europium from the r-process. The abundance ratio [Eu/Ba] = +0.58 ± 0.15 dex agrees with the trend observed in metal-poor stars and is also compatible with a strong r-process contribution to the origin of the neutron-capture elements in HD 140283.

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Section: Comparison With Previous Resultsmentioning

confidence: 99%

Origin of the heavy elements in HD 140283

Mello¹,

Barbuy²,

Spite³

et al. 2012

A&A

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“…For comparison with our results, we have retained only the disk stars with metallicities [Fe/H] ≥ −1.00 and with accurate determinations of Eu abundances (i.e., those not marked by ":" in their tables). HFSs were calculated by the authors using data from Becker et al (1993) and Broström et al (1995), as we did, but they simplified the adopted structure by grouping close-by components together, like S85. Spectral synthesis was employed to analyse the same line we used.…”

Section: Europiummentioning

confidence: 99%

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

Peloso¹,

Cunha²,

Silva³

et al. 2005

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We present Mn, Co and Eu abundances for a sample of 20 disk F and G dwarfs and subgiants with metallicities in the range −0.8 ≤ [Fe/H] ≤ +0.3. We investigate the influence of hyperfine structure (HFS) on the derived abundances of Mn and Co by using HFS data from different sources in the literature, as well as calculated HFS from interaction factors A and B. Eu abundances were obtained from spectral synthesis of one Eu  line that takes into account HFS from a series of recent laboratory measurements. For the lines analysed in this study, we find that for manganese, the differences between abundances obtained with different HFSs are no greater than 0.10 dex. Our cobalt abundances are even less sensitive to the choice of HFS than Mn, presenting a 0.07 dex maximum difference between determinations with different HFSs. However, the cobalt HFS data from different sources are significantly different. Our abundance results for Mn offer an independent confirmation of literature results, favouring type Ia supernovae as the main nucleosynthesis site of Mn production, in contrast to trends of Mn versus metallicity previously reported in the literature. The observed discrepancies may be attributed to the lack of HFS in the works we used for comparison. Our results for Eu are in accordance with low-mass type II supernovae being the main site of the r-process nucleosynthesis.

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“…Also no attempt is made to analyse the isotopic splitting of 151,153 Eu; we assume a fixed 50:50 isotopic split of 151:153 when constructing the hfs-affected Eu 4129 Å line list. The Eu line list for the solar r-and s-process ratio was constructed using hfs information from Becker et al (1993) and Krebs & Winkler (1960) with log g f values taken from Biemont et al (1982). Abundances for Eu are taken as those that satisfy the χ 2 minimum.…”

Section: The [Ba/eu] Ratiomentioning

confidence: 99%

The barium isotopic fractions in five metal-poor stars

Gallagher

Ryan

Hosford

et al. 2012

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Context. Theory and observations of heavy element nucleosynthesis are in conflict with one-another. Theory states that in the most metal-poor stars, the rapid (r-) neutron-capture nucleosynthetic process would be dominant over the slow (s-) process. The most recent determinations of r-and s-process yields do not support this. Aims. We provide measurements of the Ba isotopic fractions for five metal-poor stars derived with a local thermodynamic equilibrium (LTE) analysis with 1D model stellar atmospheres. This increases the comparisons with heavy element nucleosynthesis theory. Methods. We use high resolution (R ≡ λ/Δλ = 90 000−95 000), very high signal-to-noise (S /N > 500) spectra to determine the fraction of odd Ba isotopes ( f odd ) by measuring subtle asymmetries in the profile of the Ba ii line at 4554 Å. We also use two different macroturbulent broadening techniques, Gaussian and radial-tangential, to model the Fe lines of each star, and propagate each technique to model macroturbulent broadening in the Ba 4554 Å line. We conduct a 1D non-LTE (NLTE) treatment of the Fe lines in the red giant HD 122563 and the subgiant HD 140283 in an attempt to improve the fitting. We determine [Ba/Eu] ratios for the two giants in our study, HD 122563 and HD 88609, which can also be used to determine the relative contribution of the s-and r-processes to heavy-element nucleosynthesis, for comparison with f odd . Results. We find mathematical solutions of f odd for HD 122563, HD 88609 and HD 84937 of −0.12 ± 0.07, −0.02 ± 0.09, and −0.05 ± 0.11 respectively. BD+26 • 3578 yielded a value for f odd = 0.08 ± 0.08. Only BD−04 • 3208 was found to have a physical f odd ratio of 0.18 ± 0.08. This means that all stars examined here show isotopic fractions more compatible with an s-process dominated composition. The [Ba/Eu] ratios in HD 122563 and HD 88609 are found to be −0.20 ± 0.15 and −0.47 ± 0.15 respectively, which indicate instead an r-process signature. We report a better statistical fit to the majority of Fe profiles in each star when employing a radial-tangential broadening technique during our 1D LTE investigation. Conclusions. With the increase of the number of stars for which the Ba isotope fraction f odd has been measured, and the nature of their results, there is now a stronger argument to suggest that other synthesis codes that employ alternative approaches to radiative transfer (e.g. 3D hydrodynamics) have to be considered to tackle the high level of precision required for the determination of isotopic ratios. We have shown that, from a statistical point of view, one must consider using a radial-tangential broadening technique rather than a Gaussian one to model Fe line macroturbulences when working in 1D. No improvement to Fe line fitting is seen when employing a NLTE treatment of the Fe lines.

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Hyperfine-structure measurements of theEu+151,153

Cited by 46 publications

References 17 publications

Origin of the heavy elements in HD 140283

Origin of the heavy elements in HD 140283

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

The barium isotopic fractions in five metal-poor stars

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