Intermediate star

With the core contrast (Fig. 55a) a strong peak is observed as in the case of completely labelled stars [148], while with the average contrast (Fig. 55c) the peak is less intensive. With the shell contrast (Fig. 55b) the scattering pattern is quite different. Its most important feature is the intermediate minimum, which is observed at the same Q-value, where the maxima are found for the core and average contrast conditions. 

The synthesis of the (PS)(PMMA)(PCL) 3//-ABC star has been achieved with the use of a triheterofunctional initiator (ROP, ATRP, NMP) as shown in Scheme 85 [160]. SEC characterization experiments of the different intermediates confirmed the successful synthetic procedure. 

Figure 6. T-STAR three-phase ebullated bed for hydrotreating petroleum intermediates. (From Clausen et al, 1992.)...

Open clusters (OCs) are important tools both for stellar and for galactic astrophysics, as tests of stellar evolution theory for low and intermediate mass stars and as tracers of the Galactic disk properties. Since old OCs allow us to probe the lifetime of the Milky Way disk, up to about 10 Gyr ago, they can be used to study the disk evolution with time, and in particular its chemical history. 

Abstract. We use intermediate resolution (II, 19 300) spectroscopic observations in the spectral region including the Li 6708 A line to study 341 stars in the star forming region (SFR) NGC 6530. Based on the optical color-magnitude diagrams (CMD), they are G, K and early M type pre-main sequence (PMS) cluster candidates. 72% of them are probable cluster members since are X-ray sources detected in a Chandra-ACIS observation ([2]). We use our spectroscopic measurements to confirm cluster membership by means of radial velocities and to investigate the Li abundance of cluster members. 

The conclusion is that no unevolved star shows the composition of evolved RGB stars, but rather one similar to that predicted for yields of intermediate-mass AGB stars (IM-AGB see [8]). However, since dilution with material not contaminated by CNO burning could explain the observed trends for C and N, we have to dig deeper. 

Abstract. I present preliminary results for a sample of 700 red giants in u> Cen, observed during the Ital-FLAMES Consortium GTO time in May 2003, for the Bologna Project on u Cen. Preliminary Fe and Ca abundances confirm previous results while the metal-poor and intermediate populations show a normal halo o-enhancement of [a/Fe] +0.3, the most metal-rich stars show a significantly lower [a/Fe] +0.1. If the metal-rich stars have evolved within the cluster in a process of self-enrichment, the only way to lower their a-enhancement would be SNe type la intervention. 

Theoretical models for nucleosynthesis in asymptotic giant branch stars predict a large contribution to the cosmic nitrogen abundance from intermediate-mass stars [1], In particular, hot-bottom-burning in stars above a certain mass produces [C/N] —1 [2]. However, observations of C and N abundances in C-rich, metal-poor stars, usually using the CH and CN bands, show [C/N] values that vary between —0.5 and 1.5. (Fig. 1). If any of these stars have been polluted by intermediate mass AGB stars, then they should have lower [C/N] ratios. However, most of the CH stars with detailed abundances have [C/Fe] > 1.0, and it is more likely than stars mildly enhanced in C have been polluted by N-rich stars. 

R.Pallavicini, S. Randich, P. Sestito Lithium abundances in intermediate age and old clusters . In 13th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, ed. by F. Favata et al. (ESA, Special Publication), in press (2004)... 

Abstract. We present the results of a spectroscopic analysis of bright stars in the Carina dSph galaxy. We collected low-resolution FORS2 VLT spectra of ss 200 stars. Our spectroscopic targets have been selected among the evolved Carina stars, in particular we selected low-mass, old Red Giant, Asymptotic, and Horizontal Branch stars, as well as intermediate-age stars of the Red Clump. We present preliminary estimates concerning the radial velocities of old and intermediate-age populations. 

Although Ba and heavier elements seem to fit the solar r-process pattern, lighter elements show wide varieties [5]. In particular, a large dispersion has been found in [Sr/Ba] at low metallicity[l], suggesting that lighter elements such as Sr does not come from a universal process, which produces Ba and Eu, but from weak r-process. An inhomogeneous chemical evolution model suggests that the dispersions in [Sr/Ba] are well-explained, when weak r-process produces 60% of Sr but only 1% of Ba in metal-poor stars. Furthermore, intermediate mass elements such as Pd must provide clues to understand the weak r-process yield. 

The interest of the astrophysical community on the evolution of the intermediate mass stars (IMS) raised in the last decades, as they have been suggested as possible responsible of the chemical anomalies which are observed in Giant and TO stars within Globular Clusters (see e.g. Gratton et al. 2004). 

Fig. 1. Abundance gradient of N/O predicted by models adopting stellar yields where rotation is not taken into account (as model 7 of [3] - thin solid line) and the same models computed with MM02 yields ([2] - thick solid line). A model where we increased only the amount of primary N in massive stars for metallicities below Z=10-B overlaps with the thick solid line shown here [1], This shows that the N/O gradient along the MW disk is affected mainly by the amount of nitrogen production in low and intermediate mass stars and not the primary N in massive stars. For the abundance data see [3] and references therein - asterisks are B stars (see Cunha, this conference).

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