Kazan state Federal University E-Archive :: Browsing by Author "Mashonkina L."

A non-LTE analysis of Mg I lines in the atmospheres of late-type stars

Mashonkina L.; Shimanskaya N.; Sakhibullin N. (1996)

The formation of Mg I lines in the atmospheres of stars with Teff = 5500-7000 K, log g = 2.0-4.5, and [A] = 0, -2 is analyzed. It is shown that the Mg I level population is a nonequilibrium one, and that overionization ...

Barium abundances in cool dwarf stars as a constraint to s- and r-process nucleosynthesis

Mashonkina L.; Gehren T.; Bikmaev I. (1999)

We revise barium abundances in 11 cool stars with metallicities ranging from -2.65 to 0.05. The results are based on differential NLTE model atmosphere analyses of spectra that have a typical S/N of 200 and a resolution ...

Barium and europium abundances in cool dwarf stars and nucleosynthesis of heavy elements

Mashonkina L.; Gehren T. (2000)

We revise barium abundances in 29 cool stars with metallicities [Fe/H] ranging from -2.20 to 0.07 and europium abundances in 15 stars with [Fe/H] from -1.52 to 0.07. The sample has been extracted from Fuhrmann's lists ...

Determination of non-LTE barium abundances in solar-type stars: A technique for non-LTE calculations

Mashonkina L.; Bikmaev I. (1996)

Detailed statistical-equilibrium calculations are performed for the Ba II ion to elucidate the influence of non-LTE effects on barium abundances in the atmospheres of stars with Teff = 5500-6500 K, log g = 4.0 and 4.5, and ...

Effects of spot structure of lines of rare earths and non-LTE effects on lithium abundance estimates for two roAp stars

Mashonkina L.; Shavrina A.; Khalack V.; Polosukhina N.; Tsymbal V.; Vygonets V. (2002)

Taking into account blending of the lithium 6108 Å line profile by adjacent rare-earth lines together with their spotted surface structure does not appreciably affect lithium abundance estimates for the atmospheres of HD ...

Eu III oscillator strengths and Europium abundances in Ap stars

Mashonkina L.; Ryabtsev A.; Ryabchikova T. (2002)

We present our calculations of the spectrum and oscillator strengths for the 4f7 - (4f65d + 4f66s) Eu III transitions. The calculations were performed with Cowan's RCN-RCG-RCE codes in the single-configuration approximation. ...

Heavy element abundances in cool dwarf stars: An implication for the evolution of the Galaxy

Mashonkina L.; Gehren T. (2001)

We present revised strontium, barium and europium abundances for 63 cool stars with metallicities [Fe/H] ranging from -2.20 to 0.25. The stellar sample has been extracted from Fuhrmann's lists (1998, 2001). It is confined ...

Lithium on the surface of cool magnetic CP stars. II. Spectrum analysis of HD 83368 and HD 60435 with lithium spots

Shavrina A.; Polosukhina N.; Zverko J.; Mashonkina L.; Khalack V.; Ziznovský J.; Hack M.; Tsymbal V.; North P.; Vygonec V. (2001)

As a further step in our Lithium project we present results of abundance determination of some elements in the roAp star HD 60435. Possible NLTE effects were considered. Equivalent widths of spectral lines vary with ...

Magnesium abundances in mildly metal-poor stars from different indicators

Abia C.; Mashonkina L. (2004)

We present Mg abundances derived from high-resolution spectra using several MgI and two high-excitation Mg II lines for 19 metal-poor stars with [Fe/H] values between -1.1 and +0.2. The main goal is to search for systematic ...

Mg, Ba and Eu abundances in thick disk and halo stars

Mashonkina L.; Gehren T.; Travaglio C.; Borkova T. (2003)

Our sample of cool dwarf stars from previous papers (Mashonkina & Gehren 2000, 2001) is extended in this study including 15 moderately metal-deficient stars. The samples of halo and thick disk stars have overlapping ...

Neutron-capture elements in halo, thick-disk, and thin-disk stars. Strontium, yttrium, zirconium, cerium

Mashonkina L.; Vinogradova A.; Ptitsyn D.; Khokhlova V.; Chernetsova T. (2007)

We derived Sr, Y, Zr, and Ce abundances for a sample of 74 cool dwarfs and subgiants with iron abundances, [Fe/H], between 0.25 and -2.43. These estimates were obtained using synthetic spectra, assuming local thermodynamic ...

Neutron-Capture Elements in Halo, Thick-Disk, and Thin-Disk Stars: Neodymium

Mashonkina L.; Kamaeva L.; Samotoev V.; Sakhibullin N. (2004)

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to -1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ ≃ ...

Non-LTE analyses of strontium abundances in stars: A stars

Belyakova E.; Mashonkina L.; Sakhibullin N. (1999)

The formation of SrII lines in the atmospheres of stars of various types in the absence of local thermodynamic equilibrium (LTE) is analyzed. Departures from LTE are insignificant for normal-metallicity stars with T eff ≤ ...

Non-LTE analysis of the formation of EuII lines in the atmospheres of solar-type stars

Mashonkina L. (2000)

A method to analyze the statistical equilibrium of the EuII ion based on a 36-level model atom has been developed. The formation of EuII lines without assuming local thermodynamic equilibrium (LTE) is considered for Teff ...

Non-LTE effects in Mg I lines for various types of stars

Shimanskaya N.; Mashonkina L.; Sakhibullin N. (2000)

We have performed a detailed statistical-equilibrium analysis based on a 49-level model of the magnesium atom for the atmospheres of stars of various spectral types: Teff = 4500-12000 K, logg = 0.0 - 4.5, and [M/H] = 0 to ...

Non-LTE effects in Na I spectral lines in stellar atmospheres

Mashonkina L.; Shimanskiǐ V.; Sakhibullin N. (2000)

The paper examines the statistical equilibrium of Na I in stellar atmospheres with a wide range of parameters: Teff = 4000-12 500 K, log g = 0.0-4.5, and heavy element content [A] from 0.5 to -4.0. The effect of the ...

On the problem of selective enhancement of barium in the atmospheres of baii stars

Mashonkina L.; Začs L. (1996)

High-resolution spectroscopy and standard LTE analysis of 31 barium and normal red giants (Astron. Astrophys. 283, 1994, p. 937) shows a selective enhancement of Ba (∼ +0.5 dex) in two stars. HR3845 and HD130386, relative ...

Revised magnesium abundances in galactic halo and disk stars

Shimanskaya N.; Mashonkina L. (2001)

A differential analysis of the magnesium abundances in 61 F-K dwarfs and subgiants with metallicities -2.6 < [Fe/H] < +0.2 is performed based on published observational data. Fundamental parameters for 36 stars are determined: ...

Statistical equilibrium of Sr II in the atmospheres of F and G stars

Belyakova E.; Mashonkina L. (1997)

The statistical equilibrium of Sr II in the atmospheres of stars with T eff = 5500-6500 K, logg = 1.0-4.5, and [M/H] from 0 to -3 has been analyzed for the first time. For Sr II, the pumping of excited states by chains of ...

The atmospheric lithium abundances of solar analogues

Galeev A.; Bikmaev I.; Mashonkina L.; Musaev F.; Galazutdinov G. (2004)

We have analyzed the lithium abundance in the atmospheres of 20 stars that are solar analogues based on high-resolution echelle spectra using model atmospheres in a non-LTE approach. In terms of their lithium abundances, ...

Browsing by Author "Mashonkina L."

Browsing by Author "Mashonkina L."

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