The Remarkable Deaths of 9–11 Solar Mass Stars (original) (raw)
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Advanced Burning Stages and Fate of 8-10M☉STARS
The Astrophysical Journal, 2013
The stellar mass range 8 M/M 12 corresponds to the most massive AGB stars and the most numerous massive stars. It is host to a variety of supernova progenitors and is therefore very important for galactic chemical evolution and stellar population studies. In this paper, we study the transition from super-AGB star to massive star and find that a propagating neon-oxygen burning shell is common to both the most massive electron capture supernova (EC-SN) progenitors and the lowest mass iron-core collapse supernova (FeCCSN) progenitors. Of the models that ignite neon burning off-center, the 9.5 M star would evolve to an FeCCSN after the neon-burning shell propagates to the center, as in previous studies. The neon-burning shell in the 8.8 M model, however, fails to reach the center as the URCA process and an extended (0.6 M) region of low Y e (0.48) in the outer part of the core begin to dominate the late evolution; the model evolves to an EC-SN. This is the first study to follow the most massive EC-SN progenitors to collapse, representing an evolutionary path to EC-SN in addition to that from SAGB stars undergoing thermal pulses. We also present models of an 8.75 M super-AGB star through its entire thermal pulse phase until electron captures on 20 Ne begin at its center and of a 12 M star up to the iron core collapse. We discuss key uncertainties and how the different pathways to collapse affect the pre-supernova structure. Finally, we compare our results to the observed neutron star mass distribution.
The Astrophysical Journal, 2006
We calculate evolution, collapse, explosion, and nucleosynthesis of Population III very-massive stars with 500M ⊙ and 1000M ⊙ . Presupernova evolution is calculated in spherical symmetry. Collapse and explosion are calculated by a two-dimensional code, based on the bipolar jet models. We compare the results of nucleosynthesis with the abundance patterns of intracluster matter, hot gases in M82, and extremely metal-poor stars in the Galactic halo. It was found that both 500M ⊙ and 1000M ⊙ models enter the region of pair-instability but continue to undergo core collapse. In the presupernova stage, silicon burning regions occupy a large fraction, more than 20% of the total mass. For moderately aspherical explosions, the patterns of nucleosynthesis match the observational data of both intracluster medium and M82. Our results suggest that explosions of Population III core-collapse very-massive stars contribute significantly to the chemical evolution of gases in clusters of galaxies. For Galactic halo stars, our [O/Fe] ratios are smaller than the observational abundances. However, our proposed scenario is naturally consistent with this outcome. The final black hole masses are ∼ 230M ⊙ and ∼ 500M ⊙ for the 500M ⊙ and 1000M ⊙ models, respectively. This result may support the view that Population III very massive -2stars are responsible for the origin of intermediate mass black holes which were recently reported to be discovered.
The Deaths of Very Massive Stars
Very Massive Stars in the Local Universe, 2014
The theory underlying the evolution and death of stars heavier than 10 M ⊙ on the main sequence is reviewed with an emphasis upon stars much heavier than 30 M ⊙. These are stars that, in the absence of substantial mass loss, are expected to either produce black holes when they die, or, for helium cores heavier than about 35 M ⊙ , encounter the pair instability. A wide variety of outcomes is possible depending upon the initial composition of the star, its rotation rate, and the physics used to model its evolution. These heavier stars can produce some of the brightest supernovae in the universe, but also some of the faintest. They can make gammaray bursts or collapse without a whimper. Their nucleosynthesis can range from just CNO to a broad range of elements up to the iron group. Though rare nowadays, they probably played a disproportionate role in shaping the evolution of the universe following the formation of its first stars.
Evolution and Explosion of Very Massive Primordial Stars
ESO ASTROPHYSICS SYMPOSIA
While the modern stellar IMF shows a rapid decline with increasing mass, theoretical investigations suggest that very massive stars (100 M⊙) may have been abundant in the early universe. Other calculations also indicate that, lacking metals, these same stars reach their late evolutionary stages without appreciable mass loss. After central helium burning, they encounter the electron-positron pair instability, collapse, and burn oxygen and silicon explosively. If sufficient energy is released by the burning, these stars explode as brilliant supernovae with energies up to 100 times that of an ordinary core collapse supernova. They also eject up to 50 M⊙ of radioactive 56 Ni. Stars less massive than 140 M⊙ or more massive than 260 M⊙ should collapse into black holes instead of exploding, thus bounding the pair-creation supernovae with regions of stellar mass that are nucleosynthetically sterile. Pair-instability supernovae might be detectable in the near infrared out to redshifts of 20 or more and their ashes should leave a distinctive nucleosynthetic pattern.
Chemical ejecta and final fates of intermediate-mass and massive stars
2017
In my PhD work I carried out a detailed investigation on the final fates and chemical ejecta produced by intermediate-mass and massive stars. The first part of the thesis is focused on massive and very massive stars. We derive the ejecta for a large number of elemental species (H, He, C, N, O, F, Ne, Na, Mg, Al, Si, S Ar, K, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn) during the pre-supernova evolution and after the explosion or collapse event. We use a set of stellar tracks computed with PAdova and TRieste Stellar Evolution Code (PARSEC), with initial masses in the range between 8 M to 350 M , for thirteen different initial metallicities from Z = 0.0001 to Z = 0.02. Adopting suitable explodability criteria available in the recent literature, for each stellar model we derive the final fate and remnant mass, which critically depend on the initial mass and metallicity. Three main classes of explosion events are considered. Massive stars with initial masses from 8 Msun to 100 Msun , build a degene...
Progenitors of Core-Collapse Supernovae
Proceedings of the International Astronomical Union, 2017
Massive stars have a strong impact on their surroundings, in particular when they produce a core-collapse supernova at the end of their evolution. In these proceedings, we review the general evolution of massive stars and their properties at collapse as well as the transition between massive and intermediate-mass stars. We also summarise the effects of metallicity and rotation. We then discuss some of the major uncertainties in the modelling of massive stars, with a particular emphasis on the treatment of convection in 1D stellar evolution codes. Finally, we present new 3D hydrodynamic simulations of convection in carbon burning and list key points to take from 3D hydrodynamic studies for the development of new prescriptions for convective boundary mixing in 1D stellar evolution codes.
Evolution of Massive Stars Up to the End of Central Oxygen Burning
The Astrophysical Journal, 2004
We present a detailed study of the evolution of massive stars of masses 15, 20, 25 and 30 M ⊙ assuming solar-like initial chemical composition. The stellar sequences were evolved through the advanced burning phases up to the end of core oxygen burning. We present a careful analysis of the physical characteristics of the stellar models. In particular, we investigate the effect of the still unsettled reaction 12 C(α,γ) 16 O on the advanced evolution by using recent compilations of this rate. We find that this rate has a significant impact on the evolution not only during the core helium burning phase, but also during the late burning phases, especially the shell carbon-burning. We have also considered the effect of different treatment of convective instability based on the Ledoux criterion in regions of varying molecular weight gradient during the hydrogen and helium burning phases. We compare our results with other investigations whenever available. Finally, our present study constitutes the basis of analyzing the nucleosynthesis processes in massive stars. In particular we will present a detail analysis of the s-process in a forthcoming paper.
2018
The work reported in this dissertation concern the study of kinetics, cycles and quantum mechanic processes of nuclear reactions involved in massive stars together with explosive nucleosynthesis phenomena having a key role in supernovae explosion. Four main fields are explored: physics of nuclear reaction, hydrogen burning, CNO cycles and explosive supernovae phenomena. The first chapter provide an overview of the background of the nuclear physics and of the potential approaches to the field as quantum mechanic aspects, cross section and Maxwell-Boltzmann distribution. The next chapter describe the hydrogen burning processes for stars with low mass (our sun), the CNO and hot CNO cycles involved for higher mass stars and other cycles as sodium and magnesium. The third chapter review the helium burning process involved in Red Giants as result of the exhausted hydrogen fuel. A short overview of other helium processes is briefly discussed. The fourth chapter provide a summary of the accepted model of explosive burning process involved in supernovae explosion. Explosive nucleosynthesis together with heavy elements as silicon burning processes are also described.
Evolution and Explosion of Massive Stars
Annals of the New York Academy of Sciences, 1980
*Work performed under the auspices of the U S. Department of Energy by the UCLLL under ?Work performed in part under NSF contract No. AST-76-10933. Present address is contract number W-7405-ENG-48.
Single and binary evolution of Population III stars and their supernovae explosions
We present stellar evolution calculations for Population III stars for both single and binary star evolution. Our models include 10 M and 16.5 M single stars and a 10 M model star that undergoes an episode of accretion resulting in a final mass of 16.1 M . For comparison, we present the evolution of a solar heavy element abundance model. We use the structure from late stage evolution models to calculate simulated supernova light curves. Light curve comparisons are made between accretion and non-accretion progenitor models, and models for single star evolution of comparable masses. Where possible, we make comparisons to previous works. Similar investigations have been carried out, but primarily for solar or near solar heavy metal abundance stars and not including both the evolution and supernovae explosions in one work.