Electronegativity in the local density functional formalism

Magain, Pierre; Heinrichs, J.

doi:10.1016/0038-1098(84)90149-2

Cited by 109 publications

(131 citation statements)

References 6 publications

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“…As usual, we derived values of the microturbulent velocities v t 's by eliminating trends in the relation between abundances from Fe neutral lines and expected line strength (see Magain 1984).…”

Section: Atmospheric Parametersmentioning

confidence: 99%

Na-O anticorrelation and HB

Carretta¹,

Bragaglia²,

Gratton

et al. 2009

A&A

724

851

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We present abundances of Fe, Na, and O for 1409 red giant stars in 15 galactic globular clusters (GCs), derived from the homogeneous analysis of high-resolution FLAMES/GIRAFFE spectra. Combining the present data with results from our FLAMES/UVES spectra and from previous studies within the project, we obtained a total sample of 1958 stars in 19 clusters, the largest and most homogeneous database of this kind to date. The programme clusters cover a range in metallicity from [Fe/H] = −2.4 dex to [Fe/H] = −0.4 dex, with a wide variety of global parameters (morphology of the horizontal branch, mass, concentration, etc.). For all clusters we find the Na-O anticorrelation, the classical signature of the operation of proton-capture reactions in H-burning at high temperature in a previous generation of more massive stars that are now extinct. Using quantitative criteria (from the morphology and extension of the Na-O anticorrelation), we can define three different components of the stellar population in GCs. We separate a primordial component (P) of first-generation stars, and two components of second-generation stars, that we name intermediate (I) and extreme (E) populations from their different chemical composition. The P component is present in all clusters, and its fraction is almost constant at about one third. The I component represents the bulk of the cluster population. On the other hand, E component is not present in all clusters, and it is more conspicuous in some (but not in all) of the most massive clusters. We discuss the fractions and spatial distributions of these components in our sample and in two additional clusters (M 3 = NGC 5272 and M 13 = NGC6205) with large sets of stars analysed in the literature. We also find that the slope of the anti-correlation (defined by the minimum O and maximum Na abundances) changes from cluster-to-cluster, a change that is represented well by a bilinear relation on cluster metallicity and luminosity. This second dependence suggests a correlation between average mass of polluters and cluster mass.

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Section: Atmospheric Parametersmentioning

confidence: 99%

Na-O anticorrelation and HB

Carretta¹,

Bragaglia²,

Gratton

et al. 2009

A&A

724

851

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“…4), the uncertainty on microturbulent velocity does not exceed 0.3 km/s. We have used the theoretical EWs (computed from the atomic parameters of the line and the atmospheric parameters of the star) rather than the measured values in order to avoid systematic biases on v t caused by random errors on the EW measurements (Magain, 1984). The stellar parameters can be found in Table 5. DAOSPEC returns an error estimate on the EW measurements that was propagated throughout the abundance determination.…”

Section: Determination Of Stellar Parameters and Abundancesmentioning

confidence: 99%

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

Lemasle

Hill

Tolstoy

et al. 2012

A&A

191

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Context. The ages of individual Red Giant Branch stars can range from 1 Gyr old to the age of the Universe, and it is believed that the abundances of most chemical elements in their photospheres remain unchanged with time (those that are not affected by the first dredge-up). This means that they trace the interstellar medium in the galaxy at the time the star formed, and hence the chemical enrichment history of the galaxy. Aims. Colour-Magnitude Diagram analysis has shown the Carina dwarf spheroidal to have had an unusually episodic star formation history and this is expected to be reflected in the abundances of different chemical elements. Methods. We use the VLT-FLAMES multi-fibre spectrograph in high-resolution mode (R≈20000) to measure the abundances of several chemical elements, including Fe, Mg, Ca and Ba, in a sample of 35 individual Red Giant Branch stars in the Carina dwarf spheroidal galaxy. We also combine these abundances with photometry to derive age estimates for these stars. This allows us to determine which of two distinct star formation episodes the stars in our sample belong to, and thus to define the relationship between star formation and chemical enrichment during these two episodes.

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“…According to Magain (1984), random errors on equivalent widths can cause a systematic bias in the derived microturbulence velocities. This effect is caused by the correlation of the error on each equivalent width and the abundance deduced from it, and can be avoided by using predicted equivalent widths instead of measured ones in the plot of iron abundances vs. equivalent widths.…”

Section: Spectroscopic Metallicities Temperatures and Microturbulenmentioning

confidence: 99%

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Tafelmeyer

Jablonka

Hill

et al. 2010

A&A

152

287

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We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor, and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H] < ∼ −3 and three stars are below [Fe/H] ∼ −3.5. This constitutes the first evidence that the classical dSphs Fornax and Sextans join Sculptor in containing extremely metal-poor stars and suggests that all of the classical dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H] = −3.96 ± 0.06 is the most metal-poor star ever observed in an external galaxy. We carried out a detailed analysis of the chemical abundances of the α, iron peak, and the heavy elements, and we performed a comparison with the Milky Way halo and the ultra faint dwarf stellar populations. Carbon, barium, and strontium show distinct features characterized by the early stages of galaxy formation and can constrain the origin of their nucleosynthesis.

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Electronegativity in the local density functional formalism

Cited by 109 publications

References 6 publications

Na-O anticorrelation and HB

Na-O anticorrelation and HB

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

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