71 research outputs found
Cosmological Impact Of Population III Binaries
We present the results of the stellar feedback from Population III (Pop III) binaries by employing improved, more realistic Pop III evolutionary stellar models. To facilitate a meaningful comparison, we consider a fixed mass of 60 M-circle dot incorporated in Pop III stars, either contained in a single star, or split up in binary stars of 30 M-circle dot each or an asymmetric case of one 45 and one 15 M-circle dot star. Whereas the sizes of the resulting H II regions are comparable across all cases, the He III regions around binary stars are significantly smaller than that of the single star. Consequently, the He+ 1640 angstrom recombination line is expected to become much weaker. Supernova (SN) feedback exhibits great variety due to the uncertainty in possible explosion pathways. If at least one of the component stars dies as a hypernova about 10 times more energetic than conventional core-collapse SNe, the gas inside the host minihalo is effectively blown out, chemically enriching the intergalactic medium (IGM) to an average metallicity of 10(-4)-10(-3) Z(circle dot), out to similar to 2 kpc. The single star, however, is more likely to collapse into a black hole, accompanied by at most very weak explosions. The effectiveness of early chemical enrichment would thus be significantly reduced, in contrast to. the lower mass binary stars, where at least one component is likely to contribute to heavy element production and dispersal. Important new feedback physics is also introduced if close binaries can form high-mass X-ray binaries, leading to the pre-heating and -ionization of the IGM beyond the extent of the stellar H II regions.IAU-Gruber FellowshipStanwood Johnston FellowshipKITP Graduate FellowshipDOE HEP Program DE-SC0010676NSF AST 0909129, AST-1009928, AST-1109394, PHY02-16783NASA Theory Program NNX14AH34GNASA NNX09AJ33GARC Future Fellowship FT120100363Monash University Larkins FellowshipDOE DE-GF02-87ER40328, DE-FC02-09ER41618Astronom
Pair Instability Supernovae of Very Massive Population III Stars
Numerical studies of primordial star formation suggest that the first stars
in the universe may have been very massive. Stellar models indicate that
non-rotating Population III stars with initial masses of 140-260 Msun die as
highly energetic pair-instability supernovae. We present new two-dimensional
simulations of primordial pair-instability supernovae done with the CASTRO
code. Our simulations begin at earlier times than previous multidimensional
models, at the onset of core collapse, to capture any dynamical instabilities
that may be seeded by collapse and explosive burning. Such instabilities could
enhance explosive yields by mixing hot ash with fuel, thereby accelerating
nuclear burning, and affect the spectra of the supernova by dredging up heavy
elements from greater depths in the star at early times. Our grid of models
includes both blue supergiants and red supergiants over the range in progenitor
mass expected for these events. We find that fluid instabilities driven by
oxygen and helium burning arise at the upper and lower boundaries of the oxygen
shell 20 - 100 seconds after core bounce. Instabilities driven by
burning freeze out after the SN shock exits the helium core. As the shock later
propagates through the hydrogen envelope, a strong reverse shock forms that
drives the growth of Rayleigh--Taylor instabilities. In red supergiant
progenitors, the amplitudes of these instabilities are sufficient to mix the
supernova ejecta.Comment: 42 pages, 15 figures (accepted to ApJ
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