Supernova type II

See 5 Fe (to which 5 Ni decays) for discussion of the nucleosynthesis of 5 Ni by equilibrium and quasiequilibrium processes during supernova nuclear burning. Roughly 0.5 to 0.8 solar masses of 56Ni is created by the thermonuclear explosions of white dwarfs (Type la supernovae). Only about l/loth as much is created by each core-collapse supernova (Type II), but they are about 4 to 5 times more frequent than Type la explosions. This means that about two-thirds of the galactic total of 5 Ni is synthesized by la explosions and about one-third by core-collapse Type II. 

A related question is this Which types of stars or supernova explosions produce the extinct radioactive nuclei thatare found in the solar system Here the reader is referred to the entry for each specific isotope. But this much must be appreciated first. Some radioactivities appear to be made primarily by the thermonuclear explosions of white-dwarf stars, called Type la supernovae. Others are created primarily in massive stars whose cores collapse to become neutron stars to initiate an explosive ejection (Type II supernovae). Type II supernovae occur three to five times more frequendy than do Type la supernovae. Some radioactive nuclei are made within differing portions of each event, some prior to the ejection, but some during the heat of the ejection process. And still other radioactive nuclei are created within evolved stars that do not become supernovae (red giants). This diversity of origin renders uncertain the identity of those extinct radioactivities that are to be attributed specifically to that supernova thatis supposed to have triggered the formation of the solar system. In recent scientific... 

Three sources have been proposed to produce fluorine in the Galaxy. The first was suggested by Forestini et al. (1992) and refers to production in low-mass stars during the AGB phase while two others are related to massive stars production in Wolf-Rayet stars (Meynet Arnould 2000) and in type II Supernovae, via the neutrino-induced nucleosynthesis (Woosley et al. 1990). 

The bulge sample shows enhancements in [a/Fe] at all [Fe/H] values, with the exception of a decreasing trend in [O/Fe] at high [Fe/H], The difference in [O/Fe] and [Mg/Fe] trends creates a quandary Type II models (e.g. [6]) predict that O and Mg are produced in similar mass progenitors. There are no major producers of Mg other than Type II supernovae. Therefore, why do O and Mg not show similar distributions ... 

Fig. 5.12. Calculated abundances after decay of 56Ni and other radioactive nuclei, relative to solar, in material ejected from a typical Type II supernova explosion, averaged over initial masses 10 to 50 M . Dominant isotopes of each element are circled. Adapted from Tsujimoto (1993).

The site of the r-process is also not clear, but it seems that the conditions needed to reproduce Solar-System r-process abundances may hold in the hot bubble caused by neutrino winds in the immediate surroundings of a nascent neutron star in the early stages of a supernova explosion (see Fig. 6.10). Circumstantial evidence from Galactic chemical evolution supports an origin in low-mass Type II supernovae, maybe around 10 M (Mathews, Bazan Cowan 1992 Pagel Tautvaisiene 1995). Another possibility is the neutrino-driven wind from a neutron star formed by the accretion-induced collapse of a white dwarf in a binary system (Woosley Baron 1992) leading to a silent supernova (Nomoto 1986). In stars with extreme metal-deficiency, the heavy elements sometimes display an abundance pattern characteristic of the r-process with little or no contribution from the s-process, and the... 

Assuming the star formation rate for the Galaxy given in Table 7.9 and that all stars between 10 and 100 M explode as Type II supemovae, estimate the corresponding supernova rates for the IMFs in Table 7.8. How much difference does it make if the upper mass limit for SN is 50 M (The observed rate for SN II in galaxies like our own is of the order of 2 to 3 per century.)... 

Assuming a continuous and homogeneous galactic wind with a mass flux rja, iff (rj = const.), combined with a selective (metal-enhanced) wind r/ x the mass of Type II supernova ejecta (tj = const. < 1), show that Eq. (8.6) for the Simple model is replaced by... 

Each star follows a different path and at a different rate. Ageing stars turn red, except for the most massive, which become violet or even ultraviolet, gradually moving away from the main sequence. Their core temperatures and pressures increase, thereby triggering further nuclear reactions which can build carbon from helium as the stars ascend the giant branch. The construction of nuclear species in massive stars reaches its apotheosis in the explosion of type II supernovas. 

In the case of rapid capture, several neutrons are added before conversions of type n p bring the neutron to proton ratio back to reasonable proportions. The r process requires impressive neutron fluxes and extreme densities and temperatures that can only be achieved in type II supernovas or the coalescence of two neutron stars. The details are not yet understood. However, we have no other explanation for the existence of gold and heavy isotopes of tin ( Sn and " Sn), for example. There is another process, namely photodisintegration, which is very short-lasting and leads to nuclei poor in neutrons, or rich in protons (referred to as a p process). 

Heavy nucleus abundances in ancient stars are determined by rapid neutron capture, very probably associated with type II supernovas. 

It is worth noting in passing that the ratios O/Fe, Mg/Fe, Si/Fe, Ca/Fe and Ti/Fe in the ejected matter are roughly three times greater than their solar counterparts. These excesses of a nuclei are observed in ancient stars of the galactic halo, suggesting that the explosion of massive stars (type II supernovas) may have produced them (see Chapter 8). 

The yield table thus serves as a basis for modelling the chemical evolution of our Galaxy, or any other galaxy. Three distinct components must be specified the yields of massive stars (8-100 Mq), which become type II supernovas, those of intermediate-mass stars (1-8 Mq), which blossom into planetary nebulas, and finally, those of overfed white dwarfs, which give birth to type la supernovas. 

Mochkovitch R. (1994) An introduction to the physics of type II supernova explosions , in Matter under Extreme Conditions (Springer-Verlag, Berhn). 

A model of hydrostatic nucleosysnthesis(Thielemann and Arnett, 1985) suggests that 2,Si and 3 Si are mainly produced in He, C, Ne burning, and that a smaller relative abundance of (2,Si) / C3°Si D than solar is expected. Recent models of supernova explosion indicate that expected relative abundance of C2,Si) / C3 °Si is 0.1 for type II supernovae(Nomoto et al., 1984) and 0.8 for type II supernovae (Woosley and Weaver, 1986). These models cannot explain the observed excess of 2,Si. 

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