A new multiplet table for Fe I

Nave, Gillian; Johansson, Sveneric; Learner, R. C. M.; Thorne, A. P.; Brault, J. W.

doi:10.1086/192079

Cited by 340 publications

(352 citation statements)

References 29 publications

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“…To provide close collisional coupling of Fe i to the continuum electron reservoir and consequently establish a realistic ionization balance between the neutral and singly-ionized species, the energy separation of the highest levels in the model atom from the ionization limit must be smaller than the mean kinetic energy of electrons, i.e., 0.5 eV for atmospheres of solar temperature. In our earlier study (Gehren et al 2001a, hereafter Paper I), the model atom of Fe i was built up using all the energy levels from the experimental analysis of Nave et al (1994), in total 846 levels with an excitation energy, E exc , up to 7.5 eV. The later updates of Schoenfeld et al (1995) and the measurements of Brown et al (1988) provided another 112 energy levels for Fe i.…”

Section: Model Atommentioning

confidence: 99%

A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

Mashonkina

Gehren

Shi

et al. 2011

A&A

233

266

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Aims. We evaluate non-local thermodynamical equilibrium (non-LTE) line formation for the two ions of iron and check the ionization equilibrium between Fe i and Fe ii in model atmospheres of the cool reference stars based on the best available complete model atom for neutral and singly-ionized iron.Methods. We present a comprehensive model atom for Fe with more than 3000 measured and predicted energy levels. As a test and first application of the improved model atom, iron abundances are determined for the Sun and five stars with well determined stellar parameters and high-quality observed spectra. The efficiency of inelastic collisions with hydrogen atoms in the statistical equilibrium of iron is empirically estimated from inspection of their different influence on the Fe i and Fe ii lines in the selected stars. Results. Non-LTE leads to systematically depleted total absorption in the Fe i lines and to positive abundance corrections in agreement with the previous studies, however, the magnitude of such corrections is smaller compared to the earlier results. These non-LTE corrections do not exceed 0.1 dex for the solar metallicity and mildly metal-deficient stars, and they vary within 0.21 dex and 0.35 dex in the very metal-poor stars HD 84937 and HD 122563, respectively, depending on the assumed efficiency of collisions with hydrogen atoms. Based on the analysis of the Fe i/Fe ii ionization equilibrium in these two stars, we recommend to apply the Drawin formalism in non-LTE studies of Fe with a scaling factor of 0.1. For the Fe ii lines non-LTE corrections do not exceed 0.01 dex in absolute value over the whole range of stellar parameters that are considered. This study reveals two problems. The first one is that g f -values available for the Fe i and Fe ii lines are not accurate enough to pursue high-accuracy absolute stellar abundance determinations. For the Sun, the mean non-LTE abundance obtained from 54 Fe i lines is 7.56 ± 0.09 and the mean abundance from 18 Fe ii lines varies between 7.41 ± 0.11 and 7.56 ± 0.05 depending on the source of the g f -values. The second problem is that lines of Fe i give, on average, a 0.1 dex lower abundance compared with those of Fe ii lines for HD 61421 and HD 102870, even when applying a differential line-by-line analysis with regard to the Sun. A disparity between neutral atoms and first ions points to problems of stellar atmosphere modelling or/and effective temperature determination.

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Section: Model Atommentioning

confidence: 99%

A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

Mashonkina

Gehren

Shi

et al. 2011

A&A

233

266

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“…λ 0 is the central laboratory wavelength of each spectral line. σ and α represent the cross-section (in units of Bohr's radius squared a 2 0 ) and velocity parameter of the atom undergoing the transition, respectively, for collisions with neutral atoms under the ABO theory (Anstee & O'Mara 1995;Barklem & O'Mara 1997;Barklem et al 1998 Nave et al (1994). b Values taken from Borrero et al (2003).…”

Section: Gregor'smentioning

confidence: 99%

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Borrero

Ramos

Collados

et al. 2016

A&A

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Context. Some models for the topology of the magnetic field in sunspot penumbrae predict the existence of field-free or dynamically weak-field regions in the deep Photosphere. Aims. To confirm or rule out the existence of weak-field regions in the deepest photospheric layers of the penumbra. Methods. The magnetic field at log τ5 = 0 is investigated by means of inversions of spectropolarimetric data of two different sunspots located very close to disk center with a spatial resolution of approximately 0.4-0.45 ′′ . The data have been recorded using the GRIS instrument attached to the 1.5-meters GREGOR solar telescope at El Teide observatory. It includes three Fe i lines around 1565 nm, whose sensitivity to the magnetic field peaks at half a pressure-scale-height deeper than the sensitivity of the widely used Fe i spectral line pair at 630 nm. Prior to the inversion, the data is corrected for the effects of scattered light using a deconvolution method with several point spread functions. Results. At log τ5 = 0 we find no evidence for the existence of regions with dynamically weak (B < 500 Gauss) magnetic fields in sunspot penumbrae. This result is much more reliable than previous investigations done with Fe i lines at 630 nm. Moreover, the result is independent of the number of nodes employed in the inversion, and also independent of the point spread function used to deconvolve the data, and does not depend on the amount of straylight (i.e. wide-angle scattered light) considered.

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“…We note that the relative HFS component wavelengths-measured from FTS spectra-are more accurate than this in all cases. The absolute wavelengths of the wavelength standard lines ( Fe i: Learner & Thorne 1988, Nave et al 1994Ti ii: Pickering et al 2001, 2002) have a reported absolute accuracy in their FTS measurements of $AE0.001 cm À1 (P0.3 m8) in our wavelength regions. The uncertainties from our wavelength scale and co-addition of individual orders are no larger than AE0.9 m8, and we have verified that, after the wavelength solution has been applied, the Th-Ar emission lines are correctly identified to within $AE1 m8.…”

Section: Set the Absolute Wavelength Scale From Nearby Wavelength Stamentioning

confidence: 55%

Europium, Samarium, and Neodymium Isotopic Fractions in Metal‐Poor Stars

Roederer¹,

Lawler²,

Sneden³

et al. 2008

AIP Conference Proceedings

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We have derived isotopic fractions of europium, samarium, and neodymium in two metal-poor giants with differing neutron-capture nucleosynthetic histories. These isotopic fractions were measured from new high-resolution (R $ 120;000), high signal-to-noise ratio (S/N $ 160Y1000) spectra obtained with the 2d-coudé spectrograph of McDonald Observatory's 2.7 m Smith telescope. Synthetic spectra were generated using recent high-precision laboratory measurements of hyperfine and isotopic subcomponents of several transitions of these elements and matched quantitatively to the observed spectra. We interpret our isotopic fractions by the nucleosynthesis predictions of the stellar model, which reproduces s-process nucleosynthesis from the physical conditions expected in low-mass, thermally pulsing stars on the AGB, and the classical method, which approximates s-process nucleosynthesis by a steady neutron flux impinging on Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with an r-process origin by the classical method and is consistent with either an r-or an s-process origin by the stellar model. Our Sm isotopic fraction in HD 175305 suggests a predominantly r-process origin, and our Sm isotopic fraction in HD 196944 is consistent with an s-process origin. The Nd isotopic fractions, while consistent with either r-process or s-process origins, have very little ability to distinguish between any physical values for the isotopic fraction in either star. This study for the first time extends the n-capture origin of multiple rare earths in metal-poor stars from elemental abundances to the isotopic level, strengthening the r-process interpretation for HD 175305 and the s-process interpretation for HD 196944.

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A new multiplet table for Fe I

Cited by 340 publications

References 29 publications

A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps

Europium, Samarium, and Neodymium Isotopic Fractions in Metal‐Poor Stars

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