The bottom panel is a zoom of the upper one and makes clear that there exists a discrepancy between the yttrium lines of the two stars. Zoom In Zoom Out Reset image size. The upper plot shows the agreement between the two spectra, as a consequence of the similarity in the stellar parameters. In this study we analyzed singly ionized lines for all the elements. Hence, they might also operate below the dredge-up in the interpulse phases of AGB stars, where nuclear sources are not present. Shortland Street 2nd October – Dailymotion.

Producing 13 C in the He intershell during the interpulse periods requires the injection of protons from the envelope into layers below those fully mixed by the third dredge-up, through some form of extra-mixing. The bottom panel is a zoom of the upper one and makes clear that there exists a discrepancy between the yttrium lines of the two stars. Members of this cluster are characterized by a dispersion in both yttrium and cerium, ranging from moderate to extreme enrichment. Similar to Figure 4 , but measurements from the literature are also shown. References for atomic parameters: Random errors include the contributions from errors of EW measurements and from uncertainties of stellar parameters. Also, and most important, the adopted ages for the clusters we study are on the same scale as those of D’Orazi et al. The spectra of the stars in these clusters were all collected with UVES consistently with the rest of the sample.

Busso 1,2L. We have already started new calculations with this specific scope. Column 11 shows yttrium abundances derived through all available lines.

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You will need to select episove minimum of one corridor. The figure suffers from low number statistics, in particular at large Galactocentric distances. In this study we analyzed singly ionized lines for all the elements. Table 4 shows the presence of one anomalous star, which is significantly more s -element enriched than the other members of the same cluster. All recent searches will be deleted. Details on the observations and instrument configuration can be found in Pace et al.

We can derive their age through solid and homogeneous estimates. Filled symbols denote dwarf stars, while open symbols indicate giant cluster members. Note that cluster ages are or have been put by us on the same scale as that used for the OCs discussed in this paper. Since a larger amount of iron and oxygen makes the occurrence of the third dredge-up in AGB stars more difficult and reduces neutron exposure see Straniero et al. Specifically, we find that clusters older than about 1. In Section 3 we sgb our main results.


Our results necessarily require that very low mass asymptotic giant branch stars M 1. Shortland Street 11th November HD.

As an example, it is known that the Ba abundance observed in the Galactic halo is primarily synthesized by the r -process. We suggest that it might not be intrinsic in part.

We underline that all the stellar parameters of this study were determined spectroscopically. On the other hand, and as is expected from an analysis based on lines from ionized elements, a 0. Shortland Street 19th November Randich 3M. We underline the high relevance for our analysis of the rather detailed knowledge achieved for OCs.

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All the lines were inspected very carefully on 620 UVES spectrum of the Sun, and, in particular, the presence of possible blends was checked.

This neutron source is actually the dominant one for all intermediate-mass Lugaro et al. For three of the sample clusters, measurements of one or more of the elements analyzed in this paper are available in the literature, namely M67 Tautvaisiene et al. Several recent studies focusing on abundance determinations in OCs include the measurement of one or more s -process elements.

Nevertheless, the figure shows an overall fair agreement, as data from the literature follow the same trend displayed by our own measurements. Also for the Sun, abundances were derived from EW measurements using the MOOG code Sneden ; we adopted the version and the grid of one-dimensional local thermal equilibrium model atmospheres by Kurucz This is certainly conditioned by what we know of the solar composition and does wgb necessarily apply to the Galaxy as a whole.

As is usually done, errors due to uncertainties in stellar parameters were estimated epixode varying each parameter separately while leaving the others unchanged. This suggests that the further increase in barium found by D’Orazi et al.


This site uses cookies. On the other hand, three clusters epissode ages around 0. We interpret its anomaly as the consequence episoxe a mass-transfer episode in a binary system, from a more massive, evolved companion that had already produced s -elements. Further investigations on s -element abundances in outer OCs are required and could become relevant clues for the knowledge of these external zones of the disk and their evolution. To find out more, see our Privacy and Cookies policy.

For one cluster only, M67, more than one s -process determination is available in the literature. Shortland Street Episode – 22 October A preliminary discussion of the expected consequences is presented in Section 4and some conclusions are drawn in Section 5.

This, in turn, makes clear that there is a need for an s -element production from very low mass AGB stars with large ages, hence capable of affecting young clusters, not old ones more effective than previously imagined. Therefore, these few peculiar cases have a vanishingly small effect on our general trends, so that we can conclude that they do not affect in any significant way our con- clusions.

Most noticeably, two different gradients actually seem to be present. Shortland Street Episode – 6 November One is traced by older OCs open circles of the figureand one characterizes the younger objects filled circles. While new measurements of Zr and of the other s -process elements for all these clusters are needed, we conclude that the data from the literature generally confirm xgb main results of our paper.

Also, and most important, the adopted ages for the clusters we study are on the same scale as those of D’Orazi et al. The growth previously suggested for Ba is confirmed for all the elements analyzed in our study. A possible explanation could be related to the infall process that occurred during the disk formation.