Stellar nucleosynthesis in the Galactic history : the carbon

stars

In the light of recent results on their nature, their origin and their

possible relation with stars of population III (still undiscovered!),

I will present results from high resolution chemical analysis

of a large sample of metal-poor carbon enhanced stars.

I will first demonstrate the impact of molecules on the

thermal structure of the atmosphere, on photometry and on the abundance

determination.

I will then discuss abundance results from the extended sample. I will

especially focus on the heavy element abundances. It appears indeed that

carbon enhanced stars split into two groups: stars only enriched in s-

elements and stars enriched both in s- and r-elements.

Finally, from the chemical analysis we have carried out, it turns out

that our sample includes also a thermal pulsing asymptotic giant branch

star, with an extremely low content of metals, making it the most

evolved star among metal-poor stars.

Best regards

Thomas Masseron