Presupernova Evolution with Improved Rates for Weak Interactions

By Alexander Heger, Stan Woosley, G. Mart'inez-Pinedo, K. L. Ucsc, Aarhus Universitet, Denmark. 2000

164 citations recorded by the source corpus.

Recent shell-model calculations of weak-interaction rates for nuclei in the mass range A = 45-65 have resulted in substantial revisions to the hitherto standard set of Fuller, Fowler, & Newman (FFN). In particular, key electron-capture rates, such as that for 60Co, are much smaller. We consider here the effects of these revised rates on the presupernova (post-oxygen burning) evolution of massive stars in the mass range 11-40 M☉. Moreover, we include, for the first time in models by our group, the effects of modern rates for beta decay in addition to electron capture and positron emission. Stars of 15, 25, and 40 M☉ are examined in detail using both the full FFN rate set and the revised rates. An additional finely spaced (in mass) grid of 34 models is also calculated in order to give the systematics of iron core and silicon core masses. Values for the central electron mole number at the time of iron core collapse in the new models are typically larger, by ΔYe = 0.005-0.015, than those of Woosley & Weaver, with a tendency for the more massive models to display larger differences. About half of this change is a consequence of including beta decay; the other half, the result of the smaller rates for electron capture. Unlike what might be expected solely on basis of the larger Ye values, the new iron core masses are systematically smaller owing to a decrease in the entropy in the outer iron core. The changes in iron core mass range from zero to 0.1 M☉ (larger changes for high-mass stars). It would be erroneous however to estimate the facility of exploding these new models based solely upon their iron core mass since the entire core structure is altered and the density change is not so different as the adjustments in composition might suggest. We also observe, as predicted by Aufderheide et al., a tendency toward beta equilibrium just prior to the collapse of the core, and the subsequent loss of that equilibrium as core collapse proceeds. This tendency is more pronounced in the 15 M☉ model than in the heavier stars. We discuss the key weak reaction rates, both beta decay and electron capture, responsible for the evolution of Ye and make suggestions for future measurements.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/6114c53e629fe3248a4010b7bdfd7e499bebbfcf

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Citations in the corpus

Nucleosynthesis in Massive Stars with Improved Nuclear and Stellar Physics (2001, methodology): “Weak rates and weak neutrino losses in the late evolution stages now use the rates of Langanke & Mart́ınez-Pinedo (2000; see Heger et al. 2001a,b).”
Nucleosynthesis-relevant conditions in neutrino-driven supernova outflows. I. Spherically symmetric (2006, methodology): “…we discuss six different models: two (T10-l1-r1 and T10-l2-r1) are based on a 10.2 M star (data provided by A. Heger, priv. comm.), three (T15-l2-r1, T15-l1-r1, and T15-l1r0) on a 15 M progenitor (s15s7b2, Woosley & Weaver 1995), and one (T25-l5-r4) on a 25 M progenitor (s25a28, Heger et al. 2001).”
MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): BINARIES, PULSATIONS, AND EXPLOSIONS (2015, methodology): “The 204 isotope network, mesa 204.net, used in the calculation is listed in Table 2, and includes the isotopes identified in Heger et al. (2001) as important for Ye in core-collapse models.”
Nuclear weak-interaction processes in stars (2002, background): “It is, however, related to changes in the entropy profile during silicon shell burning which reduces the growth of the iron core just prior to collapse (Heger et al., 2001a).”
THE REMARKABLE DEATHS OF 9–11 SOLAR MASS STARS (2015, background): “Here, as in past studies (Woosley & Heger 2007; Heger et al. 2001), the ground state decay rates were taken as a lower bound to be used at low temperature and density.”
Explosion mechanism, neutrino burst and gravitational wave in core-collapse supernovae (2005, methodology): “According to Heger et al [124, 125], who studied the effect of the shell model rates on presupernova models by repeating the calculations of Woosley and Weaver (1995) [363] while fixing the other stellar physics, the iron core mass is found to be reduced about up to 0.2M⊙ than the ones in Woosley an”
Abundances of Cu and Zn in metal-poor stars: Clues for Galaxy evolution (2002, result): “…and 0.05 dex for Cu abundance; (6) – Total error. the input physics and in reaction rates have somewhat alleviated the difficulties, as compared to the original calculations by Woosley & Weaver (1995), but the problems are not solved (Hoffman et al. 2001; Heger et al. 2001; Rauscher et al. 2002).”