Pair creation supernovae at low and high redshift (original) (raw)
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Proceedings of the International Astronomical Union, 2011
Using a population number synthesis code with detailed binary evolution, we calculate the distribution of the number of type Ia supernovae as a function of time after starburst. This is done for both main progenitor scenarios (single degenerate and double degenerate), but also with various evolutionary assumptions (such as mass transfer efficiency, angular momentum loss, and common envelope description). The comparison of these theoretically predicted delay time distributions with observations in elliptical galaxies then allows to constrain the evolutionary scenarios and parameters. From the morphological shape of the distributions, we conclude that all supernovae Ia cannot be produced through the single degenerate scenario alone, with the best match being obtained when both scenarios contribute. Within the double degenerate scenario, most systems go through a phase of quasi-conservative, stable Roche lobe overflow. We propose stellar rotation as a possible solution for the underestimation of the observed absolute number of events, as is the case in many theoretical population synthesis studies. A brief comparison with these other studies is made, showing good correspondence under the nontrivial condition of equivalent assumptions. We also investigate the influence of different supernova Ia progenitors and evolutionary parameters on the theoretical distribution of the iron abundance of G-type dwarfs in the Galactic disk. These stars are good indicators of the entire chemical history of the Galaxy, and their predicted metallicity distribution can also be compared to the observational ones. This again limits the number of acceptable combinations of assumptions. Supporting previous results, the best correspondence is found in the case where both the single and double degenerate scenario contribute.
Evolution of the First Stellar Generations
Although the theoretical study of very low metallicity (Z) and metal-free stars is not new, their importance has recently greatly increased since two related fields have been developing rapidly. The first is cosmological simulations of the formation of the first stars and of the reionisation period. The second is the observations of extremely metal poor stars. In this paper, we present pre-supernova evolution models of massive rotating stars at very low Z (Z = 10 −8 ) and at Z = 0. Rotation has a strong impact on mass loss and nucleosynthesis. Models reaching break-up velocities lose up to ten percents of their initial mass. In very low Z models, rotational and convective mixing enhances significantly the surface content in carbon, nitrogen and oxygen (CNO) when the star becomes a red supergiant. This induces a strong mass loss for stars more massive than about 60 M⊙. Our models predict type Ib,c supernovae and gamma-ray bursts at very low Z. Rotational mixing also induces a large production of CNO elements, in particular of primary nitrogen. The stellar wind chemical composition is compatible with the most metal-poor star know to date, HE 1327-2326, for CNO elements. Our models reproduce the early evolution of nitrogen in the Milky Way.
Stellar Evolution at Low Metallicity
Massive stars played a key role in the early evolution of the Universe. They formed with the first halos and started the re-ionisation. It is therefore very important to understand their evolution. In this review, we first recall the effect of metallicity (Z) on the evolution of massive stars. We then describe the strong impact of rotation induced mixing and mass loss at very low Z. The strong mixing leads to a significant production of primary 14 N, 13 C and 22 Ne. Mass loss during the red supergiant stage allows the production of Wolf-Rayet stars, type Ib,c supernovae and possibly gamma-ray bursts (GRBs) down to almost Z = 0 for stars more massive than 60 M⊙. Galactic chemical evolution models calculated with models of rotating stars better reproduce the early evolution of N/O, C/O and 12 C/ 13 C. Finally, the impact of magnetic fields is discussed in the context of GRBs.
The Nucleosynthetic Imprint of 15-40 Solar Mass Primordial Supernovae on Metal-Poor Stars
2009
The inclusion of rotationally-induced mixing in stellar evolution can alter the structure and composition of presupernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine piston-driven spherical explosions in 15, 25 and 40 M ⊙ stars at Z = 0 and 10 −4 Z ⊙ with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants (in contrast to the blue supergiant progenitors made without rotation). On the other hand, the Z = 10 −4 Z ⊙ models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal free stars than the Z = 10 −4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and at constant explosion energy, less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557-4840, with a zero metallicity 15 M ⊙ , 2.4 × 10 51 erg supernova. A Salpeter IMF averaged integration of our yields for Z = 0 models with explosion energies of 2.4 × 10 51 ergs or less is in good agreement with the abundances observed in larger samples of extremely metal-poor stars, provided 15 M ⊙ stars are included. Since the abundance patterns of extremely metal-poor stars likely arise from a representative sample of progenitors, our yields suggest that 15-40 M ⊙ core-collapse supernovae with moderate explosion energies contributed the bulk of the metals to the early universe.
Stellar Evolution in the Early Universe
Massive stars played a key role in the early evolution of the Universe. They formed with the first halos and started the re-ionisation. It is therefore very important to understand their evolution. In this paper, we describe the strong impact of rotation induced mixing and mass loss at very low Z. The strong mixing leads to a significant production of primary 14 N, 13 C and 22 Ne. Mass loss during the red supergiant stage allows the production of Wolf-Rayet stars, type Ib,c supernovae and possibly gamma-ray bursts (GRBs) down to almost Z = 0 for stars more massive than 60 M⊙. Galactic chemical evolution models calculated with models of rotating stars better reproduce the early evolution of N/O, C/O and 12 C/ 13 C. We calculated the weak s-process production induced by the primary 22 Ne and obtain overproduction factors (relative to the initial composition, Z = 10 −6 ) between 100-1000 in the mass range 60-90.
The Nucleosynthetic Imprint of 15–40 M ☉ Primordial Supernovae on Metal-Poor Stars
The Astrophysical Journal, 2010
The inclusion of rotationally-induced mixing in stellar evolution can alter the structure and composition of presupernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine piston-driven spherical explosions in 15, 25 and 40 M ⊙ stars at Z = 0 and 10 −4 Z ⊙ with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants (in contrast to the blue supergiant progenitors made without rotation). On the other hand, the Z = 10 −4 Z ⊙ models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal free stars than the Z = 10 −4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and at constant explosion energy, less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557-4840, with a zero metallicity 15 M ⊙ , 2.4 × 10 51 erg supernova. A Salpeter IMF averaged integration of our yields for Z = 0 models with explosion energies of 2.4 × 10 51 ergs or less is in good agreement with the abundances observed in larger samples of extremely metal-poor stars, provided 15 M ⊙ stars are included. Since the abundance patterns of extremely metal-poor stars likely arise from a representative sample of progenitors, our yields suggest that 15-40 M ⊙ core-collapse supernovae with moderate explosion energies contributed the bulk of the metals to the early universe.
The cosmic rate of supernovae and the range of stars ending as Type Ia SNe
2000
The present cosmic rate of Type Ia supernovae (SNeIa) suggests that about 6% of all stars in binary systems with primaries in the initial mass range 3 − 9 M⊙ end up as SNeIa. If that is confirmed, the unavoidable conclusion is that SNeIa can only be explained by the single degenerate scenario. At most 1% of stars in binary systems in the above range end up as CO + CO WD pairs, with total mass equal to or larger than the Chandrasekhar mass. Given that the number of mergers from pairs of CO + He WDs that reach the Chandrasekhar mass is even lower, the conclusion strongly favors binaries containing just one CO WD as the progenitors of SNeIa, since the SNeIa production efficiency (relative to the instantaneous star formation rate) predicted for double degenerate (DD) pairs lies more than 3σ below the observational data, and the DD scenario can be rejected at more than 99% confidence level. Only if the SFR measurements from z ∼ 0.1 to z ∼ 0.5 are being underestimated by a factor of 6 while SNeIa rates are not, can we escape the above conclusion. We evaluate the numbers and characteristics of double WD systems with different chemical compositions (CO and He WDs) that should form and compare them with the observations, in order to check our predictions. Our conclusions appear robust after that test.
Observational constraints on the progenitor metallicities of core-collapse supernovae★
Monthly Notices of the Royal Astronomical Society, 2010
We present constraints on the progenitor metallicities of core-collapse supernovae. To date, nearly all metallicity constraints have been inferred from indirect methods such as metallicity gradients in host galaxies, luminosities of host galaxies, or derived global galaxy metallicities. Here, progenitor metallicities are derived from optical spectra taken at the sites of nearby supernovae, from the ratio of strong emission lines found in their host HII regions. We present results from the spectra of 74 host HII regions and discuss the implications that these have on the nature of core-collapse supernova progenitors. Overall, while we find that the mean metallicity of type Ibc environments is higher than that of type II events, this difference is smaller than observed in previous studies. There is only a 0.06 dex difference in the mean metallicity values, at a statistical significance of ∼ 1.5 σ, while using a KS-test we find that the two metallicity distributions are marginally consistent with being drawn from the same parent population (probability >10%). This argues that progenitor metallicity is not a dominant parameter in deciding supernovae type, with progenitor mass and/or binarity playing a much more significant role. The mean derived oxygen metallicities (12+log(O/H)) for the different supernova types, on the Pettini & Pagel (2004) scale are; 8.580 (standard error on the mean of 0.027) for the 46 type II supernovae (dominated by type II plateau); 8.616 (0.040) for 10 type Ib; and 8.626 (0.039) for 14 type Ic. Overall the types Ibc supernovae have a mean metallicity of 8.635 (0.026, 27 supernovae). Hence we find a slight suggestion of a metallicity sequence, in terms of increasing progenitor metallicity going from type II through Ib and finally Ic supernovae arising from the highest metallicity progenitors. Finally we discuss these results in the context of all current literature progenitor metallicity measurements, and discuss biases and selection effects that may affect the current sample compared to overall supernova and galaxy samples.
Stellar Evolution and the Cosmologial Supernovae Rates
Galaxy Evolution: Connecting the Distant Universe with the Local Fossil Record, 1999
We present the results of the population synthesis of the population of the supernovae progenitors. Both single and double degenerate progenitors of SN Ia are considered. We compute the cosmic rate histories for SN I, SN II and both classes of SN Ia, and present them in the form of redshift and magnitude distributions. These results can be compared with observational data, allowing to estimate the star formation rate history and the cosmological parameters including baryons which cannot be estimated from analysing the Hubble diagrams of supernovae.
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.