Origin of the elements  Which reactions  Which physical conditions  Which astrophysical sites  Which quantities Yields depend on reaction rates, M, Z, treatment of convection, Mass loss, V rot, B magn, Interactions in close binaries, Explosion mechanism Explosive nucleosynthesis 1D-3D models Nomoto et al (ARAA) Evolution of stellar systems Part of history hidden in the abundances of the elements.

How to constrain the yields? INDVIDUAL STARS  Check of in situ processes (WR)  Composition of the ejecta of Supernovae  Asteroseismology  Unaltered surface composition of stars composed from ISM enriched by one or two nucleosynthetic events or a restricted mass range of stars like EMP halo stars, CEMP stars  General properties of stars COLLECTIVE EFFECTS  ISM abundances (in primordial galaxies) Nomoto et al (ARAA)

STRIKING OBSERVATIONAL FACTS (EMP STARS) 1) Scatter: different according to the elements considered Cayrel et al ) No sign of Pair Instability Supernovae 3) Important amount of primary nitrogen 4) More carbon, less oxygen produced at low Z ? 5) CEMP, CRUMP (no, r, s, r and s) 6) The O-Na, Mg-Al anticorrelation in globular cluster stars 7) Helium-rich stars in globular clusters Israelian et al. 2004, Centurion et al 2003Spite et al 2005Norris et al 1997 Mc William et al 95; Barbuy et al. 96; Christlieb et al. 04; Frebel et al. 05; Plez & Cohen 05 Gratton et al 2004; Piotto et al 2005 Observations:

IN THE FIELD IN GLOBULAR CLUSTERS IN THE HALO TWO KINDS OF CHEMICALLY PECULIAR STARS STARS MADE OF H- and He-burning productsH-burning products Norris et al 97 Gratton et al Large scatter

SAME MASS: 60 M sol, SAME V ini =800 km s - 1 Z= Z= Slow wind: MS Only enriched in H-burning products Slow wind: YSG enriched in H- and He-burning products

WW95 CL04 Netal06 V=0, Hetal05 V=300, Hetal05