Atomic data from the IRON project

Meléndez, M.; Bautista, M. A.; Badnell, N. R.

doi:10.1051/0004-6361:20077262

Cited by 50 publications

(46 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Meléndez et al (2007) and Bautista et al (2002), respectively. For Li I, Mg I, Al I, and Si I inelastic collisions with neutral hydrogen particles are treated using accurate rate coefficients from quantum mechanical calculations of Belyaev & Barklem (2003), Barklem et al (2012), Belyaev (2013), and Belyaev et al (2014), respectively.…”

Section: Nlte Methodsmentioning

confidence: 99%

SYSTEMATIC NON-LTE STUDY OF THE −2.6 ≤ [Fe/H] ≤ 0.2 F AND G DWARFS IN THE SOLAR NEIGHBORHOOD. II. ABUNDANCE PATTERNS FROM Li TO Eu*

Zhao

Mashonkina

Yan

et al. 2016

ApJ

147

158

View full text Add to dashboard Cite

For the first time, we present an extensive study of stars with individual non-LTE (NLTE) abundances for 17 chemical elements from Li to Eu in a sample of stars uniformly distributed over the −2.62 [Fe/H] +0.24 metallicity range that is suitable for the Galactic chemical evolution research. The star sample has been kinematically selected to trace the Galactic thin and thick disks and halo. We find new results and improve earlier ones as follows: (i) the element-to-iron ratios for Mg, Si, Ca, and Ti form a metal-poor (MP) plateau at a similar height of 0.3 dex, and the knee occurs at common

show abstract

Section: Nlte Methodsmentioning

confidence: 99%

SYSTEMATIC NON-LTE STUDY OF THE −2.6 ≤ [Fe/H] ≤ 0.2 F AND G DWARFS IN THE SOLAR NEIGHBORHOOD. II. ABUNDANCE PATTERNS FROM Li TO Eu*

Zhao

Mashonkina

Yan

et al. 2016

ApJ

147

158

View full text Add to dashboard Cite

show abstract

“…Photoionization cross-sections are from the Opacity project. Collisional excitation rates are from Meléndez et al (2007) extrapolated beyond the tabulated temperature range of 3000 K to 38 000 K using Burgess & Tully (1992). Collisional ionization rates from the ground state are from Arnaud & Rothenflug (1985) and from excited states we use the general formula provided by Burgess & Chidichimo (1983).…”

Section: Calciummentioning

confidence: 99%

Approximations for radiative cooling and heating in the solar chromosphere

Carlsson

Leenaarts

2012

A&A

185

163

View full text Add to dashboard Cite

Context. The radiative energy balance in the solar chromosphere is dominated by strong spectral lines that are formed out of LTE. It is computationally prohibitive to solve the full equations of radiative transfer and statistical equilibrium in 3D time dependent MHD simulations. Aims. We look for simple recipes to compute the radiative energy balance in the dominant lines under solar chromospheric conditions. Methods. We use detailed calculations in time-dependent and 2D MHD snapshots to derive empirical formulae for the radiative cooling and heating. Results. The radiative cooling in neutral hydrogen lines and the Lyman continuum, the H and K and intrared triplet lines of singly ionized calcium and the h and k lines of singly ionized magnesium can be written as a product of an optically thin emission (dependent on temperature), an escape probability (dependent on column mass) and an ionization fraction (dependent on temperature). In the cool pockets of the chromosphere the same transitions contribute to the heating of the gas and similar formulae can be derived for these processes. We finally derive a simple recipe for the radiative heating of the chromosphere from incoming coronal radiation. We compare our recipes with the detailed results and comment on the accuracy and applicability of the recipes.

show abstract

“…Collisional rates between the ground level and the ten lower levels of Ca I were taken from Samson & Berrington (2001). For Ca II, collisional rates were taken from Meléndez et al (2007) instead of those of Burgess et al (1995) used by Mashonkina et al (2007) for the lower seven terms.…”

Section: Atomic Modelmentioning

confidence: 99%

NLTE determination of the calcium abundance and 3D corrections in extremely metal-poor stars

Spite

Andrievsky

Spite

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Calcium is a key element for constraining the models of chemical enrichment of the Galaxy. Aims. Extremely metal-poor stars contain the fossil records of the chemical composition of the early Galaxy and it is important to compare Ca abundance with abundances of other light elements, that are supposed to be synthesized in the same stellar evolution phases. Methods. The NLTE profiles of the calcium lines were computed in a sample of 53 extremely metal-poor stars with a modified version of the program MULTI, which allows a very good description of the radiation field.Results. With our new model atom we are able to reconcile the abundance of Ca deduced from the Ca I and Ca II lines in Procyon. This abundance is found to be solar.-We find that [Ca/Fe] = 0.50 ± 0.09 in the early Galaxy, a value slightly higher than the previous LTE estimations.-The scatter of the ratios [X/Ca] is generally smaller than the scatter of the ratio [X/Mg] where X is a "light metal" (O, Na, Mg, Al, S, and K) with the exception of Al. These scatters cannot be explained by error of measurements, except for oxygen. Surprisingly, the scatter of [X/Fe] is always equal to, or even smaller than, the scatter around the mean value of [X/Ca].-We note that at low metallicity, the wavelength of the Ca I resonance line is shifted relative to the (weaker) subordinate lines, a signature of the effect of convection.-The Ca abundance deduced from the Ca I resonance line (422.7 nm) is found to be systematically smaller at very low metallicity, than the abundance deduced from the subordinate lines. Our computations of the effects of convection (3D effects) are not able to explain this difference. A fully consistent 3D NLTE model atmosphere and line formation scheme would be necessary to fully capture the physics of the stellar atmosphere.

show abstract

Atomic data from the IRON project

Cited by 50 publications

References 54 publications

SYSTEMATIC NON-LTE STUDY OF THE −2.6 ≤ [Fe/H] ≤ 0.2 F AND G DWARFS IN THE SOLAR NEIGHBORHOOD. II. ABUNDANCE PATTERNS FROM Li TO Eu*

SYSTEMATIC NON-LTE STUDY OF THE −2.6 ≤ [Fe/H] ≤ 0.2 F AND G DWARFS IN THE SOLAR NEIGHBORHOOD. II. ABUNDANCE PATTERNS FROM Li TO Eu*

Approximations for radiative cooling and heating in the solar chromosphere

NLTE determination of the calcium abundance and 3D corrections in extremely metal-poor stars

Contact Info

Product

Resources

About