Sulphur abundance in Galactic stars

Caffau, E.; Bonifacio, P.; Faraggiana, R.; François, P.; Gratton, R.; Barbieri, M.

doi:10.1051/0004-6361:20052905

Cited by 95 publications

(146 citation statements)

References 50 publications

(177 reference statements)

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“…We adopt the log g f values of the NIST database, which holds the values of Wiese et al (1969), which are experimental but D quality, corresponding to a possible error up to 50% (see Table 1 for the values). A thorough discussion of the available values for S i atomic data is avilable Caffau et al (2005b).…”

Section: Discussionmentioning

confidence: 99%

“…Due to the radial velocity of the clusters, the line that happens to be the most often unblended is the one at 922.8 nm, that is, the line laying on the wing of the hydrogen Paschen ζ line. The measurement of the equivalent width (EW) of lines falling on the wings of broad features is not easy, and produces a value that is usually lower than the true EW by about 5% (Caffau et al 2005b). To determine the sulfur abundance a line profile fitting procedure is to be preferred taking the profile of the Paschen ζ into account.…”

Section: Discussionmentioning

confidence: 99%

“…To keep the analysis as homogeneous as possible, we nevertheless decided to determine the sulfur abundance using line profile fitting for all the unblended features. Such fitting was performed by means of the code described in Caffau et al (2005b). In the fitting procedure, the line broadening was kept fixed at the instrumental level (7 km s −1 ).…”

Section: Discussionmentioning

confidence: 99%

“…Caffau et al 2007a;Ryde 2006;Caffau et al 2005b;Korn & Ryde 2005;Nissen et al 2004;Ryde & Lambert 2004, among the most recent), but agreement on its behavior at low metallicities has not been reached yet. While some of the cited authors (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…While some of the cited authors (e.g. Nissen et al 2007) find that S follows the same trend as other α-elements ( [S/Fe] showing a plateau at low metallicities), others point towards a steady growth in [S/Fe] with decreasing metallicity (Israelian & Rebolo 2001;Takada-Hidai et al 2002), or an increase in the scatter of [S/Fe] at low [Fe/H] (Caffau et al 2005b). The cited debate can in fact be extended to the overall behavior of α-elements.…”

Section: Introductionmentioning

confidence: 99%

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Sulfur in the globular clusters 47 Tucanae and NGC 6752

Sbordone

Limongi

Chieffi

et al. 2009

A&A

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Context. The light elements Li, O, Na, Al, and Mg are known to show star-to-star variations in the globular clusters 47 Tuc and NGC 6752. Such variations are interpreted as coming from processing in a previous generation of stars. Aims. In this paper we investigate the abundances of the α-element sulfur, for which no previous measurements exist. In fact this element has not been investigated in any Galactic globular cluster so far. The only globular cluster for which such measurements are available is Terzan 7, which belongs to the Sgr dSph.Methods. We use high-resolution spectra of the S i Mult. 1, acquired with the UVES spectrograph at the 8.2 m VLT-Kueyen telescope, for turn-off and giant stars in the two globular clusters. The spectra were analysed making use of ATLAS static plane parallel model atmospheres and SYNTHE spectrum synthesis. We also compute 3D corrections from CO 5 BOLD hydrodynamic models and apply corrections due to NLTE effects taken from the literature. Results. In the cluster NGC 6752 sulfur has been measured only in four subgiant stars. We find no significant star-to-star scatter and a mean [S/Fe] = +0.49 ± 0.15, consistent with what is observed in field stars of the same metallicity. In the cluster 47 Tuc we measured S in 4 turn-off and 5 subgiant stars with a mean [S/Fe] = +0.18 ± 0.14. While this result is compatible with no star-to-star scatter we notice a statistically significant correlation of the sulfur abundance with the sodium abundance and a tentative correlation with the silicon abundance. Conclusions. The sulfur-sodium correlation is not easily explained in terms of nucleosynthesis. An origin due to atomic diffusion can be easily dismissed. The correlation cannot be easily dismissed either, in view of its statistical significance, until better data for more stars is available.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sulfur in the globular clusters 47 Tucanae and NGC 6752

Sbordone

Limongi

Chieffi

et al. 2009

A&A

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Prospects of stellar abundance studies from near‐IR spectra observed with the E‐ELT

Ryde

2010

Astron Nachr

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In 2006 ESO Council authorized a Phase B study of a European AO-telescope with a 42 m segmented primary with a 5-mirror design, the E-ELT. Several reports and working groups have already presented science cases for an E-ELT, specifically exploiting the new capabilities of such a large telescope. One of the aims of the design has been to find a balance in the performances between an E-ELT and the James Webb Space Telescope, JWST. Apart from the larger photon-collecting area, the strengths of the former is the higher attainable spatial and spectral resolutions. The E-ELT AO system will have an optimal performance in the near-IR, which makes it specially advantageous. High-resolution spectroscopy in the near-infrared has, however, not been discussed much. This paper aims at filling that gap, by specifically discussing spectroscopy of stellar (mainly red giant), photospheric abundances. Based on studies in the literature of stellar abundances, at the needed medium to high spectral resolutions in the near-infrared (0.8 − 2.4 µm), I will try to extrapolate published results to the performance of the E-ELT and explore what could be done at the E-ELT in this field. A discussion on what instrument characteristics that would be needed for stellar abundance analyses in the near-IR will be given.

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Sulphur abundances in halo stars from multiplet 3 at 1045 nm

Caffau¹,

Sbordone

Ludwig

et al. 2010

Astron Nachr

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Sulphur is a volatile α-element which is not locked into dust grains in the interstellar medium (ISM). Hence, its abundance does not need to be corrected for dust depletion when comparing the ISM to the stellar atmospheres. The abundance of sulphur in the photosphere of metal-poor stars is a matter of debate: according to some authors, [S/Fe] versus [Fe/H] forms a plateau at low metallicity, while, according to other studies, there is a large scatter or perhaps a bimodal distribution. In metal-poor stars sulphur is detectable by its lines of Mult. 1 at 920 nm, but this range is heavily contaminated by telluric absorptions, and one line of the multiplet is blended by the hydrogen Paschen ζ line. We study the possibility of using Mult. 3 (at 1045 nm) for deriving the sulphur abundance because this range, now observable at the VLT with the infra-red spectrograph CRIRES, is little contaminated by telluric absorption and not affected by blends at least in metal-poor stars. We compare the abundances derived from Multiplets 1 and 3, taking into account NLTE corrections and 3D effects. Here we present the results for a sample of four stars, although the scatter is less pronounced than in previous analysis, we cannot find a plateau in [S/Fe], and confirm the scatter of the sulphur abundance at low metallicity.

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Sulphur abundance in Galactic stars

Cited by 95 publications

References 50 publications

Sulfur in the globular clusters 47 Tucanae and NGC 6752

Sulfur in the globular clusters 47 Tucanae and NGC 6752

Prospects of stellar abundance studies from near‐IR spectra observed with the E‐ELT

Sulphur abundances in halo stars from multiplet 3 at 1045 nm

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