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The final fate of very massive first stars

Keywords: first stars - stars: population iii, stellar evolution, mass loss, final fate.

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Abstract:

a generation of stars which formed from primordial nearly pure h/he gas, the so-called first stars or population iii stars, must have existed since heavy elements can only be synthesized in the interior of the stars. these stars were responsible for the initial heavy elements enrichment of the intergalactic medium. in this work we analyze the possible outcome of the evolution of very massive population iii stars and whether their final fate can avoid the pair instability supernovae explosion. we have recently calculated the evolution and nucleosynthesis of mass losing very massive population iii stars during the hydrogen and helium burning phases, and proposed a new scenario for the first stars in the universe. according to this scenario, the first stars were born very massive, but evolve with mass loss, and its possible endpoint is a hypernovae stage. at low metallicity the effects on the presupernova structure depends on the initial mass and the mass loss rate during the main sequence evolution. presupernova stars of lower metallicity have different characteristics depending if they are galactic or pregalactic, and if they evolve without or with mass loss. when these stars evolve with mass loss, their convective core size increase and their helium- or carbon-oxygen core mass decreases. then, the stars could explode like hypernovae or supernovae.

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