On the establishment of internally consistent abundance-oscillator strength scales

Gurtovenko, É. A.; Костик, Р. І.

doi:10.1007/3-540-09737-6_44

Cited by 14 publications

(20 citation statements)

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“…This leaves the blended lines uncovered by the laboratory measurements. To improve the quality of the numerous (but inaccurate) g f -values provided by the theoretical computations, some authors calibrate the oscillator strengths by setting the g fvalues to match the strength of the synthetic line with the corresponding line in the Sun spectrum (among others Gurtovenko & Kostik 1981Thévenin 1989Thévenin , 1990Borrero et al 2003), in two stars like the Sun and Arcturus (Kirby et al 2008;Boeche et al 2011) or in three stars like the Sun, Procyon and Eri (Lobel et al 2011). Recently, Martins et al (2014) used the spectra of three different stars (the Sun, Arcturus, and Vega) and a statistical technique (the cross-entropy algorithm) to recover the oscillator strengths and broadening parameters that minimize the difference between the observed spectra and the synthetic ones.…”

Section: The Log Gf Calibration Proceduresmentioning

confidence: 99%

SP_Ace: a new code to derive stellar parameters and elemental abundances

Boeche

Grebel

2016

A&A

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Context. Ongoing and future massive spectroscopic surveys will collect large numbers (10 6 -10 7 ) of stellar spectra that need to be analyzed. Highly automated software is needed to derive stellar parameters and chemical abundances from these spectra. Aims. We developed a new method of estimating the stellar parameters T eff , log g, [M/H], and elemental abundances. This method was implemented in a new code, SP_Ace (Stellar Parameters And Chemical abundances Estimator). This is a highly automated code suitable for analyzing the spectra of large spectroscopic surveys with low or medium spectral resolution (R = 2000-20 000). Methods. After the astrophysical calibration of the oscillator strengths of 4643 absorption lines covering the wavelength ranges 5212-6860 Å and 8400-8924 Å, we constructed a library that contains the equivalent widths (EW) of these lines for a grid of stellar parameters. The EWs of each line are fit by a polynomial function that describes the EW of the line as a function of the stellar parameters. The coefficients of these polynomial functions are stored in a library called the "GCOG library". SP_Ace, a code written in FORTRAN95, uses the GCOG library to compute the EWs of the lines, constructs models of spectra as a function of the stellar parameters and abundances, and searches for the model that minimizes the χ 2 deviation when compared to the observed spectrum. The code has been tested on synthetic and real spectra for a wide range of signal-to-noise and spectral resolutions. Results. SP_Ace derives stellar parameters such as T eff , log g, [M/H], and chemical abundances of up to ten elements for low to medium resolution spectra of FGK-type stars with precision comparable to the one usually obtained with spectra of higher resolution. Systematic errors in stellar parameters and chemical abundances are presented and identified with tests on synthetic and real spectra. Stochastic errors are automatically estimated by the code for all the parameters. A simple Web front end of SP_Ace can be found at http://dc.g-vo.org/SP_ACE, while the source code will be published soon.

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Section: The Log Gf Calibration Proceduresmentioning

confidence: 99%

SP_Ace: a new code to derive stellar parameters and elemental abundances

Boeche

Grebel

2016

A&A

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“…Note that we did not use gf -values from Kurucz & Peytremann (1975), Kurucz & Bell (1995), or from the NIST database because they are known to produce a large scatter in the abundances inferred for various chemical elements, exceeding 1 dex in some cases (Gurtovenko & Kostik 1981;Shi et al 2008). During the last few years the experimental gf -scales of Garz (1973) and Becker et al (1980) have been used as a rule in silicon abundance determinations (Asplund 2000;Wedemeyer 2001;Shi et al 2008).…”

Section: Spectral Lines and Oscillator Strengths Used For The Abundanmentioning

confidence: 99%

Non-Lte Determination of the Silicon Abundance Using a Three-Dimensional Hydrodynamical Model of the Solar Photosphere

Shchukina

Sukhorukov

Bueno

2012

ApJ

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Confrontations of spectroscopic observations with local thermodynamic equilibrium (LTE) spectral syntheses in a three-dimensional (3D) hydrodynamical model of the solar photosphere led to a downward revision of the photospheric and meteoritic silicon abundances. Here we derive the photospheric silicon abundance taking into account non-LTE (NLTE) effects in the same 3D model. We show that the above-mentioned downward revision of the silicon abundance is caused by using the LTE approximation in the context of 3D modeling, an experimental scale of oscillator strengths, and a small number of Si i lines. We demonstrate that no revision of the solar silicon abundance is required if NLTE effects are taken into account and one uses a "solar" oscillator strength scale and an extended list of Si i lines. The NLTE abundance value we find by fitting the equivalent widths of 65 Si i lines is A NLTE Si = 7.549 ± 0.016. This value agrees well with the silicon abundance that had been recommended earlier by Grevesse & Sauval and Lodders for the solar photosphere and CI chondrite meteorites.

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“…Moore et al (1966) and Kurucz (1994). b Abundance of Fe times statistical weight of the lower level times oscillator strength from (visible lines) Gurtovenko & Kostik (1981) and from ( IR lines) Borrero et al (2003).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Quiet Sun Magnetic Fields from Simultaneous Inversions of Visible and Infrared Spectropolarimetric Observations

Cerdeña

Alméida

Kneer³

2006

ApJ

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We study the quiet Sun magnetic fields using spectropolarimetric observations of the infrared and visible Fe i lines at 6301.5, 6302.5, 15648, and 15653 8. Magnetic field strengths and filling factors are inferred by the simultaneous fit of the observed Stokes profiles under the MISMA hypothesis. The observations cover an intranetwork region at the solar disk center. We analyze 2280 Stokes profiles whose polarization signals are above noise in the two spectral ranges, which correspond to 40% of the field of view. Most of these profiles can be reproduced only with a model atmosphere including three magnetic components with very different field strengths, which indicates the coexistence of kG and sub-kG fields in our 1B5 resolution elements. We measure an unsigned magnetic flux density of 9.6 G considering the full field of view. Half of the pixels present magnetic fields with mixed polarities in the resolution element. The fraction of mixed polarities increases as the polarization weakens. We compute the probability density function of finding each magnetic field strength. It has a significant contribution of kG field strengths, which concentrates most of the observed magnetic flux and energy. This kG contribution has a preferred magnetic polarity, while the polarity of the weak fields is balanced.

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On the establishment of internally consistent abundance-oscillator strength scales

Cited by 14 publications

References 0 publications

SP_Ace: a new code to derive stellar parameters and elemental abundances

SP_Ace: a new code to derive stellar parameters and elemental abundances

Non-Lte Determination of the Silicon Abundance Using a Three-Dimensional Hydrodynamical Model of the Solar Photosphere

Quiet Sun Magnetic Fields from Simultaneous Inversions of Visible and Infrared Spectropolarimetric Observations

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