Evolution of Very Massive Population III Stars with Mass Accretion from Pre-Main Sequence to Collapse

We calculate the evolution of zero-metallicity Population III (Pop III) stars whose mass grows from the initial mass of ∼ 1M⊙ by accreting the surrounding gases. Our calculations cover a whole evolutionary stages from the pre-main sequence, via various nuclear burning stages, through the final core collapse or pair-creation instability phases. We adopt the following stellar massdependent accretion rates which are derived from cosmological simulations of early structure formation based on the low mass dark matter halos at redshifts z ∼ 20: (1) the accretion rates for the first generation (Pop III.1) stars and (2) the rates for zero-metallicity but the second generation (Pop III.2) stars which are affected by radiation from the Pop III.1 stars. For comparison, we also study the evolution with the mass-dependent accretion rates which are affected by radiatibe feedback. We show that the final mass of Pop III.1 stars can be as large as ∼ 1000M⊙, beyond the mass range (140 − 300M⊙) for the pair-instability supernovae. Such massive stars undergo core-collapse to form intermediate-mass black holes, which may be the seeds for merger trees to supermassive black holes. On the other hand, Pop III.2 stars become less massive ( ∼ < 40 − 60M⊙), being in the mass range of ordinary iron core-collapse stars. Such stars explode and eject heavy elements to contribute to chemical enrichment of the early universe as observed in the abundance patterns of extremely metal-poor stars in the Galactic halo. Subject headings: accretion, accretion disks – nuclear reactions, nucleosynthesis, abundances – stars: abundances – stars: evolution – stars: formation – supernovae: general