Carbon and nitrogen abundances in metal-poor dwarfs of the solar neighborhood

Carbon, D. F.; Barbuy, B.; Kraft, Robert P.; Friel, Eileen D.; Suntzeff, Nicholas B.

doi:10.1086/131990

Cited by 95 publications

(98 citation statements)

References 24 publications

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“…In the overlapping metallicity range, the thin disk stars reveal, on average, lower [C/Fe] ratios than the thick disk stars. In contrast, the study by Bensby & Feltzing (2006) From observations of the CH bands in 83 subdwarfs Carbon et al (1987) found [C/Fe] to be essentially constant and close to the solar value over the range −2.5 < [Fe/H] < −0.7. However, they noted an upturn in the [C/Fe] Spite et al (2005) from observations of the CH bands for the sample of 'unmixed' giant stars in the range −4 < [Fe/H] < −2.5.…”

Section: Introductionmentioning

confidence: 80%

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: Introductionmentioning

confidence: 80%

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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“…Our two most MP stars with thin-disk kinematics, HD105755 Mashonkina et al (2003). This star is also known for its extreme nitrogen overabundance, with [N/Fe] = 0.9 (Carbon et al 1987), and probably not representative of a standard evolutionary scenario for our Galaxy.…”

Section: Notes On Individual Starsmentioning

confidence: 93%

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

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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

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“…For more than 20 years, the nucleosynthetic origin of primary nitrogen, which is one of the most abundant and important elements in the Universe, for life in particular, has remained a deep mystery in astrophysics (Edmunds & Pagel 1978;Barbuy 1983;Carbon et al 1987;Thuan et al 1995;Izotov & Thuan 1999;Henry et al 2000). Nitrogen is mainly produced by the CN cycle of the CNO reactions which catalyze hydrogen burning in stars.…”

Section: The Context: Observations and Modelsmentioning

confidence: 99%

The origin of primary nitrogen in galaxies

Meynet

Maeder

2002

A&A

135

115

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Abstract. We investigate the role of stellar axial rotation on the nitrogen nucleosynthesis at low metallicities Z. For this purpose, we have calculated models with initial masses between 2 and 60 M at Z = 0.00001 from the zero age sequence to the phase of thermal pulses for models below or equal to 7 M , and up to the end of central C-burning for the more massive stars. The models include all the main physical effects of rotation. We show that intermediate mass stars with rotation naturally reproduce the occurrence and amount of primary nitrogen in the early star generations in the Universe. We identify two reasons why rotating models at low Z produce primary 14 N: 1) Since the stars lose less angular momentum, they rotate faster. Simultaneously, they are more compact, thus differential rotation and shear mixing are stronger.2) The H-burning shell has a much higher temperature and is thus closer to the core, which favours mixing between the two.

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Carbon and nitrogen abundances in metal-poor dwarfs of the solar neighborhood

Cited by 95 publications

References 24 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

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*

The origin of primary nitrogen in galaxies

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