Dispersion of Inferred SNe Ia/SNe II Ratios for Current Models of Supernova Nucleosynthesis

We have estimated the dispersion of the inferred relative frequencies of Type-Ia and TypeII supernovae (NIa/NII) in our Galaxy by fitting the numerical results of supernova nucleosynthesis to the solar-system abundances. The ratio NIa/NII is estimated to be 0.056–0.14, which is consistent with the observation, if the model of Woosley and Weaver (1995, WW95) is adopted for Type-II supernovae (SNe II). On the other hand, the upper limit of NIa/NII becomes too large for the model of Hashimoto (1995, Ha95). However, Ha95 can fit the solar values better than WW95 as far as the abundant nuclei are concerned. These results mean that Ha95 can reproduce the main nuclei of the solar-system well and that WW95 can reproduce the solar values over a wide mass-number range. We also note that NIa/NII tends to become smaller if the delayed detonation model is adopted for Type-Ia supernovae (SNe Ia). The dispersion of NIa/NII obtained in the present investigation is larger than that concluded by Tsujimoto et al. (1995), which will have an influence on the estimate of the average life time of SNe Ia’s progenitors and/or the star-formation rate history in our galaxy.