Giant star

Moreover the proportion of turnoff stars supposed to be future blue stragglers (i.e. the subturnoff-mass blue stragglers) would give an independent estimate of the ratio found by [8] the number of blue stragglers to the number of giant stars. 

Using FLAMES we observed, 45 turnoff stars, 7 giant stars with GIRAFFE (LR2 from 396.4 to 456.7 nm, R 6400 and H15 from 660.6 to 696.5 nm, R 19300). At the same time, 3 stars known as blue stragglers ([1]) were observed by UVES-link R = 47000, and a 200 nm wide spectral range centered around 580 nm. 

It is interesting to note that all stars without exception are Li rich in the initial part of this cycle, characterizing an initial Li enrichment for all stars (see Figs. 7a and 7b in Drake et al. 2002). An important test of this scenario could be the observation of separated CS around RGB giants as is the case of the more evolved carbon asymptotic giant stars. 

Red giant stars, both in the field and in globular clusters, present abundance anomalies that can not be explained by standard stellar evolution models. Some of these peculiarities, such as the decline of 12C/13C, and that of Li and 12C surface abundances for stars more luminous than the bump, clearly point towards the existence of extra-mixing processes at play inside the stars, the nature of which remains unclear. Rotation has often been invoked as a possible source for mixing inside Red Giant Branch (RGB) stars ([8], [1], [2]). In this framework, we present the first fully consistent computations of rotating low mass and low metallicity stars from the Zero Age Main Sequence (ZAMS) to the upper RGB. 

Abstract. We present preliminary results of 3D hydrodynamical simulations of surface convection in red giants stars. We investigate the main differences between static ID and 3D time-dependent model stellar atmospheres of red giants for a range of metallicities between solar and [Fe/H] = —3 focusing in particular on the impact of 3D spectral line formation on the derivation of stellar abundances. 

Boothroyd Sackmann (1999). Thus, to solve the 3He problem in terms of extra-mixing in low-mass stars, the vast majority of them (90%-100%) must be affected by this phenomenon (Galli et al. 1997). The same conclusion has been reached independently by Charbonnel do Nascimento (1998) on the basis of the statistics of carbon isotopic ratios in a sample of red-giant stars with accurate Hipparcos parallaxes. 

Much information on the theoretical and observational aspects of AGB evolution can be found in H. R. Johnson and B. Zuckerman (cds.), Evolution of Peculiar Red Giant Stars, Cambridge University Press 1989. 

Fig. 10.4. Above spectrum of the solar-type G-dwarf star HR 509 showing features of Th ii and Nd n near k 4019 A, after Butcher (1987). Th ii is blended with a strong feature due to Fe and Ni, as well as weaker features. The tracing around the zero level shows 10 x the difference between the observed spectrum (dots) and the fitted synthetic spectrum (continuous curve). Reproduced with permission from Macmillan Magazines Ltd. Below spectrum of the same region in the very metal-poor giant star CS 22892—052 ([Fe/H] —3) with a large relative excess of r-process elements ([r/Fe] = 1.7), adapted from Sneden el al. (1996).

The main s process synthesises neufron-rich nuclei with atomic number A greater than 100 and occurs in asymptotic giant branch (AGB)-type red giant stars undergoing thermal palpitations. 

Red giant stars, which are coolar than the sun, produce energy by means of the reaction jBe + H 5Li+5He+ eneiigy... 

Supercritical Mass when the quantity of a radioactive fuel is sufficient to produce a self-sustaining chain reaction Supernova massive explosion of giant star at the end of its life... 

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