Hydrogen Stark broadening calculations with the unified classical path theory

Vidal, C. R.; Cooper, J.; Smith, Elizabeth S.

doi:10.1016/0022-4073(70)90121-4

Cited by 123 publications

(58 citation statements)

References 36 publications

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“…We are using an empirical formula suggested by Peterson (1968) for computing the relative importance of the two approximations. The comparisons with more accurate numerical calculations of the Stark proÐles by Vidal, Cooper, & Smith (1970) and Stehle et al (1983) show excellent agreement. As for the numerical procedures and approximations used we started with the SYNTHE code of Kurucz (1993b) who in turn adopted the code by Peterson but also added the proper treatment of the Ðne splitting of the a lines in each series.…”

Section: Hydrogen L Ines Opacitysupporting

confidence: 52%

Model Atmospheres with Individualized Abundances

Piskunov

Kupka

2001

ApJ

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We describe a new method for computing opacity distribution functions (ODFs) for model atmosphere calculations. The method is tailored to model the atmospheres of individual stars on a modern workstation. Our goal is the computation of model atmospheres for stars with abundances signiÐcantly di †er-ent from the solar or scaled solar composition typically used for grid calculations. As a consistency test, we show that the new procedure is able to reproduce the ODFs and existing model atmospheres for solar abundances, and we describe models for stars with peculiar abundances. We demonstrate that while mild chemical peculiarities can be well represented by scaled solar models, the extreme cases result in a very di †erent atmospheric structure with no analogs in scaled solar grids. Such a structure inÑu-ences the emerging spectrum as is clearly seen both in the observed Ñux distribution and in the line ratios that are much better represented by the new models.

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Section: Hydrogen L Ines Opacitysupporting

confidence: 52%

Model Atmospheres with Individualized Abundances

Piskunov

Kupka

2001

ApJ

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“…The metallicity and microturbulence velocity from Paper II were adopted during the analysis of these Balmer lines, while the gravity was varied between log g = 1.8 and 2.4. The theoretical profiles of Hα and Hγ were computed by convolving the profiles resulting from the thermal, natural, and Stark broadening (Vidal et al 1970(Vidal et al , 1973, as well as self-broadening. For the latter, we use the selfbroadening formalism of Barklem et al (2000).…”

Section: Stellar Parameters and Atmospheric Modelsmentioning

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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“…These modern studies exploit progress in theory and experiment on line broadening to infer stellar effective temperatures from Balmer lines. Vidal et al (1970Vidal et al ( , 1973) developed a successful unified theory to model the interaction of hydrogen atoms with charged particles. Those calculations have been recently superseded by Stehlé (1994) and Stehlé & Hutcheon (1999), who have computed Stark broadened line profiles including ion dynamic effects under the model microfield method.…”

Section: Introductionmentioning

confidence: 99%

Detailed analysis of Balmer lines in cool dwarf stars

Barklem

Stempels

Prieto

et al. 2002

A&A

174

226

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Abstract. An analysis of Hα and Hβ spectra in a sample of 30 cool dwarf and subgiant stars is presented using MARCS model atmospheres based on the most recent calculations of the line opacities. A detailed quantitative comparison of the solar flux spectra with model spectra shows that Balmer line profile shapes, and therefore the temperature structure in the line formation region, are best represented under the mixing length theory by any combination of a low mixing-length parameter α and a low convective structure parameter y. A slightly lower effective temperature is obtained for the sun than the accepted value, which we attribute to errors in models and line opacities. The programme stars span temperatures from 4800 to 7100 K and include a small number of population II stars. Effective temperatures have been derived using a quantitative fitting method with a detailed error analysis. Our temperatures find good agreement with those from the Infrared Flux Method (IRFM) near solar metallicity but show differences at low metallicity where the two available IRFM determinations themselves are in disagreement. Comparison with recent temperature determinations using Balmer lines by Fuhrmann (1998Fuhrmann ( , 2000, who employed a different description of the wing absorption due to self-broadening, does not show the large differences predicted by Barklem et al. (2000b). In fact, perhaps fortuitously, reasonable agreement is found near solar metallicity, while we find significantly cooler temperatures for low metallicity stars of around solar temperature.

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Hydrogen Stark broadening calculations with the unified classical path theory

Cited by 123 publications

References 36 publications

Model Atmospheres with Individualized Abundances

Model Atmospheres with Individualized Abundances

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

Detailed analysis of Balmer lines in cool dwarf stars

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