Radiative lifetimes in Si i from laser-induced fluorescence in the visible, ultraviolet, and vacuum ultraviolet

O’Brian, Thomas R.; Lawler, J. E.

doi:10.1103/physreva.44.7134

Cited by 59 publications

(23 citation statements)

References 22 publications

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“…Our g f value for the Si i line at 3905 8 is that of NIST, which is taken from the laboratory work of Garz (1973). This is close to the value of À1.04 dex given by O'Brian & Lawler (1991), whose work is focused on the UV and hence do not reach redder than 4110 8. They report only an upper limit to the gf value for the 4103 8 line of Si i for which Cayrel et al (2003) adopt a log g f value of À3.14 dex ( F. Spite 2004, private communication), again taken from the 1973 study.…”

Section: Comparison With Cayrel Et Al (2003)supporting

confidence: 53%

Abundances In Very Metal‐Poor Dwarf Stars

Cohen

Christlieb

McWilliam

et al. 2004

ApJ

181

277

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We discuss the detailed composition of 28 extremely metal-poor (EMP) dwarfs, 22 of which are from the Hamburg / ESO Survey (HES), based on Keck echelle spectra. Our sample has a median [Fe/H] of À2.7 dex, extends to À3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK, HES) determined from low-resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below ½Fe=H ¼ À3:0 dex. So far no additional turnoff stars with ½Fe=H < À3:5 have been identified in our follow-up efforts. For the best-observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e., [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn, and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II supernovae (SNe) with a narrow range in mass and explosion parameters; high-mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small and is still dominated by measurement errors rather than intrinsic scatter. These results place strong constraints on the characteristics of the contributing SNe. The dispersion in neutron-capture elements and the abundance trends for Cr, Mn, and Co are consistent with previous studies of evolved EMP stars. We find halo-like enhancements for the -elements Mg, Ca, and Ti, but solar Si / Fe ratios for these dwarfs. This contrasts with studies of EMP giant stars, which show Si enhancements similar to other -elements. Sc/ Fe is another case where the results from EMP dwarfs and from EMP giants disagree; our Sc/ Fe ratios are enhanced compared to the solar value by $0.2 dex. Although this conflicts with the solar Sc/ Fe values seen in EMP giants, we note that -like Sc/ Fe ratios have been claimed for dwarfs at higher metallicity. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with 12 C/ 13 C $7 and with C/ N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba.

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Section: Comparison With Cayrel Et Al (2003)supporting

confidence: 53%

Abundances In Very Metal‐Poor Dwarf Stars

Cohen

Christlieb

McWilliam

et al. 2004

ApJ

181

277

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“…One clear example of such a correction are the oscillator strengths of Si I lines provided by Garz (1975) [10], which were later rescaled by O'Brian and Lawler (1991) [11]. Not only do the majority of rescaled values produce great agreement with the Paper 2 results, but they also show substantial improvements in the median offsets compared to the unscaled sources.…”

Section: Comparisons Between the Brass Results And Previously Retrievsupporting

confidence: 65%

“…References with lines belonging to several species are denoted with *. [20,21] Fe I 3 0.010 0.014 Sobeck et al (2007) [22] Cr I 14 0.020 0.055 Kostyk (1982a) [17] Ti I 7 0.020 0.018 Garz (1973) rescaled using O'Brian and Lawler (1991) [10,11] Si I 7 0.020 0.033 Blackwell et al (1986) rescaled using Grevesse et al (1989) [23,24] Ti I 3 0.020 0.037 Kostyk (1982b) [18] Ni Lennard et al (1975) [30] Ni I 3 0.050 0.087 Kostyk (1981) [16] Cr I 6 0.050 0.016 Smith and O'Neill (1975) [31] Ca I 3 0.050 0.026 Blackwell et al (1979) [32] Fe I 3 0.050 0.029 Ryabchikova et al (1999) [33] Fe II 3 0.050 0.049 Martin et al (1988) [34] Cr [41] Ni I 3 0.080 0.038 Blackwell et al (1986) [23] Ti I 12 0.080 0.037 May et al (1974) [42] Fe I 82 0.080 0.096 Kostyk and Orlova (1983) [43] Cr II/Ti II 3 0.090 0.074 Blackwell et al (1980) [44] Fe II 9 0.100 0.131 Kurucz and Bell (1995) [45] Si I 7 0.100 0.033 Garz (1973) [10] Si I 7 0.100 0.033 Wiese and Martin (1990) [46] * 25 0.100 0.243 Fuhr et al (1988) [47] Fe I/Ni I 112 0.100 0.116 …”

Section: Comparisons Between the Brass Results And Previously Retrievmentioning

confidence: 99%

The Belgian Repository of Fundamental Atomic Data and Stellar Spectra (BRASS) Identifying Fruitful Methods for Producing Atomic Data

et al. 2018

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Abstract:The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide the largest systematic and homogeneous quality assessment to-date of input atomic data required for stellar spectral synthesis. In addition to quality-assessed atomic data, BRASS shall also provide of a range of extremely high-quality benchmark stellar spectra spanning late B-type stars to early K-type stars. In this paper, we summarise the project's progress and available results to-date. We provide a brief comparison between our results and the BRASS project's compiled and cross-matched atomic literature, with the goal of providing useful feedback to the atomic community on which methods may produce more reliable and accurate atomic data. We hope that the examples presented here stimulate further investigation by the atomic physics community.

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“…Comparison of the present data with the measurements of O'Brian and Lawler [4] provides an accurate indicator of the overall uncertainties in the theoretical calculations. We find that the overall agreement between the two sets of data for the 26 fine structure transitions reported is within 5-10%, with the exception of some very weak transitions, e.g.…”

Section: Resultsmentioning

confidence: 74%

“…The fine structure ƒ-values, obtained from the length form, are then compared individually with the experimental values. The calculated and measured A-values are also given for Si I. Si I experimental data are reported by O'Brian and Lawler [4], who have measured a number of transitions using laser-induced fluorescence technique which apparently has very low uncertainties, and by Becker et al [5] who used beam-foil technique. The error bars for measured values of Si I by O'Brian and Lawler are approximate since they have been converted from ±logR 10 R (gf).…”

Section: Resultsmentioning

confidence: 99%

Transition probabilities for dipole allowed fine structure transitions in Si-like ions: Si I, S III, Ar V and Ca VII

Nahar

1993

Phys. Scr.

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Oscillator strengths and radiative transition probabilities for dipole allowed fine structure levels are obtained for Silike ions: Si I, S III, Ar V and Ca VII from multiplet line strengths calculated for the Opacity Project and using the observed energy levels. The radiative calculations are carried out in the close-coupling approximation employing the R-matrix method as developed for the Opacity Project. There are relatively little previous data available for the transition probabilities of these ions. Comparisons of the present oscillator strengths with available experimental values exhibit good agreement in general.

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Radiative lifetimes in Si i from laser-induced fluorescence in the visible, ultraviolet, and vacuum ultraviolet

Cited by 59 publications

References 22 publications

Abundances In Very Metal‐Poor Dwarf Stars

Abundances In Very Metal‐Poor Dwarf Stars

The Belgian Repository of Fundamental Atomic Data and Stellar Spectra (BRASS) Identifying Fruitful Methods for Producing Atomic Data

Transition probabilities for dipole allowed fine structure transitions in Si-like ions: Si I, S III, Ar V and Ca VII

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