Atomic transition probabilities for Dy I and Dy II

Context. The origin of carbon-enhanced metal-poor stars enriched with both s and r elements is highly debated. Detailed abundances of these types of stars are crucial to understand the nature of their progenitors. Aims. The aim of this investigation is to study in detail the abundances of SDSS J1349-0229, SDSS J0912+0216 and SDSS J1036+1212, three dwarf CEMP stars, selected from the Sloan Digital Sky Survey. Methods. Using high resolution VLT/UVES spectra (R ∼ 30 000) we determine abundances for Li, C, N, O, Na, Mg, Al, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni and 21 neutron-capture elements. We made use of CO 5 BOLD 3D hydrodynamical model atmospheres in the analysis of the carbon, nitrogen and oxygen abundances. NLTE corrections for Ci and Oi lines were computed using the Kiel code. Results. We classify SDSS J1349-0229 and SDSS J0912+0216 as CEMP-r+s stars. SDSS J1036+1212 belongs to the class CEMPno/s, with enhanced Ba, but deficient Sr, of which it is the third member discovered to date. Radial-velocity variations have been observed in SDSS J1349-0229, providing evidence that it is a member of a binary system. Conclusions. The chemical composition of the three stars is generally compatible with mass transfer from an AGB companion. However, many details remain difficult to explain. Most notably of those are the abundance of Li at the level of the Spite plateau in SDSS J1036+1212 and the large over-abundance of the pure r-process element Eu in all three stars.

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“…Oscillator strengths were adopted from Wickliffe et al (2000). Data for erbium lines were taken from Lawler et al (2008).…”

Section: Neutron-capture Elementsmentioning

confidence: 99%

Three carbon-enhanced metal-poor dwarf stars from the SDSS

Behara

Bonifacio

Ludwig

et al. 2010

A&A

135

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“…Fortunately, most neutron-capture element species considered here have been subjected to extensive laboratory investigations within the past two decades (Biémont et al 1998;Den Hartog et al 2003, 2006Ivarsson et al 2001Ivarsson et al , 2003Lawler et al 2001aLawler et al ,b,c, 2004Lawler et al , 2006Lawler et al , 2007Lawler et al , 2008Lawler et al , 2009Ljung et al 2006;Nilsson et al 2002;Wickliffe et al 2000;Xu et al 2006). We employed g f −values determined by these laboratory efforts.…”

Section: Line Selection and Atomic Datamentioning

confidence: 99%

The Hamburg/ESOR-process enhanced star survey (HERES)

Mashonkina

Christlieb

Barklem

et al. 2010

A&A

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AstrophysicsThe Hamburg/ESO R-process enhanced star survey (HERES) V ABSTRACTAims. We present a detailed abundance analysis of a strongly r-process enhanced giant star discovered in the HERES project, HE 2327−5642, for which [Fe/H] = −2.78, [r/Fe] = +0.99. Methods. We determined the stellar parameters and element abundances by analyzing the high-quality VLT/UVES spectra. The surface gravity was calculated from the non-local thermodynamic equilibrium (NLTE) ionization balance between Fe i and Fe ii, and Ca i and Ca ii.Results. Accurate abundances for a total of 40 elements and for 23 neutron-capture elements beyond Sr and up to Th were determined in HE 2327−5642. For every chemical species, the dispersion in the single line measurements around the mean does not exceed 0.11 dex. The heavy element abundance pattern of HE 2327−5642 is in excellent agreement with those previously derived for other strongly r-process enhanced stars, such as CS 22892-052, CS 31082-001, and HE 1219-0312. Elements in the range from Ba to Hf match the scaled Solar r-process pattern very well. No firm conclusion can be drawn about the relationship between the fisrt neutroncapture peak elements, Sr to Pd, in HE 2327−5642 and the Solar r-process, due to the uncertainty in the Solar r-process. A clear distinction in Sr/Eu abundance ratios was found between the halo stars of different europium enhancement. The strongly r-process enhanced stars contain a low Sr/Eu abundance ratio at [Sr/Eu] = −0.92 ± 0.13, while the stars with 0 < [Eu/Fe] < 1 and [Eu/Fe] < 0 have 0.36 dex and 0.93 dex higher Sr/Eu values, respectively. Radioactive dating for HE 2327−5642 with the observed thorium and rare-earth element abundance pairs results in an average age of 13.3 Gyr, when based on the high-entropy wind calculations, and 5.9 Gyr, when using the Solar r-residuals. We propose that HE 2327−5642 is a radial-velocity variable based on our high-resolution spectra covering ∼4.3 years.

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“…Branching fraction uncertainties are combined in quadrature with lifetime uncertainties to determine the transition-probability uncertainties in Table 2. The procedure for determining branching fraction uncertainties is described in detail by Wickli †e, Lawler, & Nave (2000). Branching fractions from a given upper level are deÐned to sum to unity ; thus, a dominant line from an upper level has a small branching fraction uncertainty almost by deÐnition.…”

Section: Branching Fraction Measurementsmentioning

confidence: 99%

“…Systematic uncertainties in the radiometric calibration are typically the most serious source of uncertainty for widely separated lines from a common upper level. Wickli †e et al (2000) tested the formula used to estimate this radiometric calibration uncertainty by comparing a large set of branching fraction measurements, covering a factor of 6 in wavelength, with an independent set of measurements. The independent measurements were made by a di †erent researcher (at NIST) using a di †erent spectrometer and a di †erent calibration technique.…”

Section: Branching Fraction Measurementsmentioning

confidence: 99%

Experimental Radiative Lifetimes, Branching Fractions, and Oscillator Strengths for Laiiand a New Determination of the Solar Lanthanum Abundance

Lawler

Bonvallet

Sneden

2001

ApJ

323

263

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Radiative lifetimes, accurate in most cases to^5%, from time-resolved laser-induced Ñuorescence measurements on a slow beam of lanthanum ions are reported for 31 odd-parity levels of La II. Experimental branching fractions for La II from emission spectra covering the near-ultraviolet to the nearinfrared are also reported. The spectra were recorded using the US National Solar Observatory 1.0 m Fourier transform spectrometer. The branching fractions are combined with the radiative lifetimes to produce 84 experimentally determined transition probabilities or oscillator strengths, generally accurate to^10%, for La II. These new experimental results are compared to older experimental and theoretical results. These data are applied to determine a new value for the solar photospheric lanthanum abundance, with estimated internal errors of^0.03 and external errors of^0.03. Slog 10 v(La)T \ 1.13,

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Atomic transition probabilities for Dy I and Dy II

Cited by 130 publications

References 19 publications

Three carbon-enhanced metal-poor dwarf stars from the SDSS

Three carbon-enhanced metal-poor dwarf stars from the SDSS

The Hamburg/ESOR-process enhanced star survey (HERES)

Experimental Radiative Lifetimes, Branching Fractions, and Oscillator Strengths for Laiiand a New Determination of the Solar Lanthanum Abundance

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