Element synthesis in the late and explosive stages of stellar evolution

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1. We have developed a computer code which can handle the massive star evolution with detail nuclear network. By this code we computed evolution of 8M <of sun> -25M <of sun> stars. For 8M <of sun> and 3.3M <of sun> helium star the mass of the iron core is 1.6M <of sun> and 1.2M <of sun> , respectively. This small iron core (1.2M <of sun> ) has special importance because the shock wave generated during the collapse stage will be able to blow up the outer region in a few millisecond. For 10-11M <of sun> stars neon burning front propagates towards the center and an explosive neon flash will be expected.2. The results from elementsynthesis of carbon burning white dwarf model for Type I supernova have been compared to the obseravtional data such as specrtum, light curve and X-ray emission. Their agreement is quite well. C+O white dwarf models as progenitor of Type I supernova have been studied. By assuming a spherical model we computed mass accretion and carbon burning When the accretion rate is greater than 2x <10^(-6)> M <of sun> <y^(-1)> , the carbon flash propagates towards the center and a neutron satr will be expected to form. We also studied non-spherical configurations. However the heavy disk formation is unlikely to occur and due to the garvitational radiation separation between two white dwarfs becomes small. Thus mass begins to flow out from the system and two white dwarfs begins to merge. But the maximum density reached is not high enough to trigger the supernova explosion.