The carbon-to-oxygen ratio in halo dwarfs

Tomkin, J.; Lemke, Michael; Lambert, David L.; Sneden, Christopher

doi:10.1086/116342

Cited by 144 publications

(177 citation statements)

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“…This is exactly the case in the Tomkin et al (1992) study. They obtained, on average, 0.4 dex higher abundance from the atomic C I compared with the molecular CH lines for the sample of metal-poor halo dwarfs.…”

Section: Introductionsupporting

confidence: 73%

Carbon abundances of reference late-type stars from 1D analysis of atomic C i and molecular CH lines

Alexeeva

Mashonkina

2015

Mon. Not. R. Astron. Soc.

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A comprehensive model atom was constructed for C I using the most up-to-date atomic data. We evaluated non-local thermodynamical equilibrium (NLTE) line formation for neutral carbon in classical 1D models representing atmospheres of late-type stars, where carbon abundance varies from solar value down to [C/H] = −3. NLTE leads to stronger C I lines compared with their LTE strength and negative NLTE abundance corrections, ∆ NLTE . The deviations from LTE are large for the strong lines in the infrared (IR), with ∆ NLTE = −0.10 dex to −0.45 dex depending on stellar parameters, and they are minor for the weak lines in the visible spectral range, with |∆ NLTE | 0.03 dex. The NLTE abundance corrections were found to be dependent of the carbon abundance in the model. As the first application of the treated model atom, carbon NLTE abundances were determined for the Sun and eight late-type stars with well-determined stellar parameters that cover the −2.56 [Fe/H] −1.02 metallicity range. Consistent abundances from the visible and IR lines were found for the Sun and the most metal-rich star of our sample, when applying a scaling factor of S H = 0.3 to the Drawinian rates of C+H collisions. Carbon abundances were also derived from the molecular CH lines and, for each star, they agree with that from the atomic C I lines. We present the NLTE abundance corrections for lines of C I in the grid of model atmospheres applicable to the carbon-enhanced (CEMP) stars.

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Section: Introductionsupporting

confidence: 73%

Carbon abundances of reference late-type stars from 1D analysis of atomic C i and molecular CH lines

Alexeeva

Mashonkina

2015

Mon. Not. R. Astron. Soc.

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“…Many authors have tried to get better estimates by multiplying the rates of Steenbock & Holweger (1984) with a factor x determined by some empirical fitting. Tomkin et al (1992) fitted the triplet lines to the solar spectrum assuming ε O = 8.92. This resulted in large collisional rates almost producing LTE.…”

Section: The Problem Of Hydrogen Collisionsmentioning

confidence: 99%

NLTE effects on oxygen lines

Kiselman

2001

New Astronomy Reviews

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“…3. In figures we also present the observational data from (Meusinger et al, 1991;Edvardsson et al, 1993;Tomkin et al, 1992) Fig. 4.…”

Section: The CD -Sph Code and Resultsmentioning

confidence: 97%

Chemo-Dynamical Evolution of Disk Galaxies, Smoothed Particles Hydrodynamics Approach

Berczik

1999

Galaxy Evolution: Connecting the Distant Universe With the Local Fossil Record

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Abstract.A new Chemo -Dynamical Smoothed Particle Hydrodynamic (CD -SPH) code is presented. The disk galaxy is described as a multi -fragmented gas and star system, embedded into the cold dark matter halo. The star formation (SF) process, SNII, SNIa and PN events as well as chemical enrichment of gas have been considered within the framework of standard SPH model. Using this model we try to describe the dynamical and chemical evolution of triaxial disk -like galaxies. It is found that such approach provides a realistic description of the process of formation, chemical and dynamical evolution of disk galaxies over the cosmological timescale.

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The carbon-to-oxygen ratio in halo dwarfs

Cited by 144 publications

References 0 publications

Carbon abundances of reference late-type stars from 1D analysis of atomic C i and molecular CH lines

Carbon abundances of reference late-type stars from 1D analysis of atomic C i and molecular CH lines

NLTE effects on oxygen lines

Chemo-Dynamical Evolution of Disk Galaxies, Smoothed Particles Hydrodynamics Approach

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