EINSTEIN
 A
 COEFFICIENTS AND OSCILLATOR STRENGTHS FOR THE
 A
 2
 Π-
 X
 2
 Σ
 +
 (RED) AND B
 2
 Σ
 +
 -X
 2
 Σ

Brooke, James S. A.; Ram, Ram S.; Western, Colin M.; Li, Gang; Schwenke, David W.; Bernath, P. F.

doi:10.1088/0067-0049/210/2/23

Cited by 141 publications

(58 citation statements)

References 78 publications

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“…comm. ), derived with similar methods and lab data as Brooke et al (2014) and Sneden et al (2014). The results of the abundance analysis are listed in Table 5.…”

Section: Abundance Measurementsmentioning

confidence: 99%

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

Skúladóttir

Tolstoy

Salvadori

et al. 2015

A&A

138

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The origin of carbon-enhanced metal-poor (CEMP) stars and their possible connection with the chemical elements produced by the first stellar generation is still highly debated. In contrast to the Galactic halo, not many CEMP stars have been found in the dwarf spheroidal galaxies around the Milky Way. Here we present detailed abundances from ESO VLT/UVES high-resolution spectroscopy for ET0097, the first CEMP star found in the Sculptor dwarf spheroidal, which is one of the best studied dwarf galaxies in the Local Group. This star has [Fe/H] = −2.03 ± 0.10, [C/Fe] = 0.51 ± 0.10 and [N/Fe] = 1.18 ± 0.20, which is the first nitrogen measurement in this galaxy. The traditional definition of CEMP stars is [C/Fe] ≥ 0.70, but taking into account that this luminous red giant branch star has undergone mixing, it was intrinsically less nitrogen enhanced and more carbon-rich when it was formed, and so it falls under the definition of CEMP stars, as proposed by Aoki et al. (2007, ApJ, 655, 492) to account for this effect. By making corrections for this mixing, we conclude that the star had [C/Fe] ≈ 0.8 during its earlier evolutionary stages. Apart from the enhanced C and N abundances, ET0097 shows no peculiarities in other elements lighter than Zn, and no enhancement of the heavier neutron-capture elements (Ba, La, Ce, Nd, Sm, Eu, Dy), making this a CEMP-no star. However, the star does show signs of the weak r-process, with an overabundance of the lighter neutron-capture elements (Sr, Y, Zr). To explain the abundance pattern observed in ET0097, we explore the possibility that this star was enriched by primordial stars. In addition to the detailed abundances for ET0097, we present estimates and upper limits for C abundances in 85 other stars in Sculptor derived from CN molecular lines, including 11 stars with [Fe/H] ≤ −2. Combining these limits with observations from the literature, the fraction of CEMP-no stars in Sculptor seems to be significantly lower than in the Galactic halo.

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“…comm. ), derived with similar methods and lab data as Brooke et al (2014) and Sneden et al (2014). The results of the abundance analysis are listed in Table 5.…”

Section: Abundance Measurementsmentioning

confidence: 99%

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

Skúladóttir

Tolstoy

Salvadori

et al. 2015

A&A

138

View full text Add to dashboard Cite

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“…comm. ), derived with similar methods and laboratory data to those in Brooke et al (2014) and Sneden et al (2014).…”

Section: Stellar Parameters and Model Atmospheresmentioning

confidence: 99%

Sulphur in the Sculptor dwarf spheroidal galaxy

Skúladóttir

Andrievsky

Tolstoy

et al. 2015

A&A

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In Galactic halo stars, sulphur has been shown to behave like other α-elements, but until now, no comprehensive studies have been done on this element in stars of other galaxies. Here, we use high-resolution ESO VLT/FLAMES/GIRAFFE spectra to determine sulphur abundances for 85 stars in the Sculptor dwarf spheroidal galaxy, covering the metallicity range −2.5 ≤ [Fe/H] ≤ −0.8. The abundances are derived from the S I triplet at 9213, 9228, and 9238 Å. These lines have been shown to be sensitive to departure from local thermodynamic equilibrium, i.e. NLTE effects. Therefore, we present new NLTE corrections for a grid of stellar parameters covering those of the target stars. The NLTE-corrected sulphur abundances in Sculptor show the same behaviour as other α-elements in that galaxy (such as Mg, Si, and Ca).

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“…In addition, we now explicitly account for the splitting in the CN R(0) feature, which is a blend of the R 1 (0) and R Q 21 (0) lines. We adopt a splitting of 0.0039Å or 0.30 km s −1 , with the former line having an f -value twice that of the latter (Federman et al 1984;Brooke et al 2014). The isotope shifts for the 13 CN and C 15 N R(0) features were held fixed at the values derived from laboratory spectroscopy.…”

Section: Observations and Data Analysismentioning

confidence: 99%

THE C ¹⁴ N/C ¹⁵ N RATIO IN DIFFUSE MOLECULAR CLOUDS

Ritchey

Federman

Lambert

2015

ApJ

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We report the first detection of C 15 N in diffuse molecular gas from a detailed examination of CN absorption lines in archival VLT/UVES spectra of stars probing local diffuse clouds. Absorption from the C 15 N isotopologue is confidently detected (at 4σ) in three out of the four directions studied and appears as a very weak feature between the main 12 CN and 13 CN absorption components. Column densities for each CN isotopologue are determined through profile fitting, after accounting for weak additional line-of-sight components of 12 CN, which are seen in the absorption profiles of CH and CH + as well. The weighted mean value of C 14 N/C 15 N for the three sight lines with detections of C 15 N is 274 ± 18. Since the diffuse molecular clouds toward our target stars have relatively high gas kinetic temperatures and relatively low visual extinctions, their C 14 N/C 15 N ratios should not be affected by chemical fractionation. The mean C 14 N/C 15 N ratio that we obtain should therefore be representative of the ambient 14 N/ 15 N ratio in the local interstellar medium. Indeed, our mean value agrees well with that derived from millimeter-wave observations of CN, HCN, and HNC in local molecular clouds.

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EINSTEIN A COEFFICIENTS AND OSCILLATOR STRENGTHS FOR THE A ² Π- X ² Σ ⁺ (RED) AND B ² Σ ⁺ -X ² Σ

Cited by 141 publications

References 78 publications

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

Sulphur in the Sculptor dwarf spheroidal galaxy

THE C ¹⁴ N/C ¹⁵ N RATIO IN DIFFUSE MOLECULAR CLOUDS

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EINSTEIN A COEFFICIENTS AND OSCILLATOR STRENGTHS FOR THE A 2 Π- X 2 Σ + (RED) AND B 2 Σ + -X 2 Σ

Cited by 141 publications

References 78 publications

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal

Sulphur in the Sculptor dwarf spheroidal galaxy

THE C 14 N/C 15 N RATIO IN DIFFUSE MOLECULAR CLOUDS

Contact Info

Product

Resources

About

EINSTEIN A COEFFICIENTS AND OSCILLATOR STRENGTHS FOR THE A ² Π- X ² Σ ⁺ (RED) AND B ² Σ ⁺ -X ² Σ

THE C ¹⁴ N/C ¹⁵ N RATIO IN DIFFUSE MOLECULAR CLOUDS