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Universality of Supernova Gamma-Process

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Universality of Supernova Gamma-Process Universality of supernova gamma-process T.Hayakawa1,2, N.Iwamoto1, T.Kajino2,3, T.Shizuma1, H.Umeda3, K.Nomoto3 1Japan Atomic Energy Agency 2National Astronomical Observatory 3University of Tokyo 1. The solar abundances give hints for stellar nucleosynthese. 2. Analyses of the p-nucleus abundances and universality for p-nuclei. 3. Mechanisms of this universality of the gamma-process 4. Extended analyses of the p-process abundances 5. A piece of evidence for weak s-process in the solar abundances. Evidence of nucleosynthesis processes in the solar abundances The solar abundances provide crucial evidence for nucleosynthesis. Evidence of the r- and s-processes Evidence of the s-process Paris of two peaks near the neutron Abundance x Neutron capture cross section magic number = constant P.A. Seeger, ApJS, 11, 121(1965). Fowler, Rev. Mod. Phy. 56, 149 (1984). Origin of p-nucleus The p-nuclei are located on the neutron-deficient side from the beta stability line. Their isotope abundances are small (typically 0.1 - 1%) The origin of the p-nuclei have been discussed over the last 50 years. Particle induced reactions in Cosmic rays, Audouze 1970 rp-Process X-ray burst in neutron stars Gamma-process: photodisintegration Disks around black holes reactions at SNe Nova, Schatz 2001 Arnould 1976, Woosley 1978 176168 HfYb 176170 HfYb 176171 HfYb 176172 HfYb s-process p-nucleus p s s+r s+r Proton Capture 176169 HfTm C/O White Dwarf s+r Solar Winds 176166 HfEr 176167 HfEr 176168 HfEr 176170 HfEr b-decay Howard 1991 s+r s+r s+r r after Neutrino-induced reactions at SNe r-process Woosley 1990 Discovery of the empirical scaling law There are 22 pairs of s- and p-nuclei with the same atomic number. pure s-nuclei 176178 HfW 176180 HfW p s+r 176180 HfTa 176181 HfTa Taking N(s)/N(p) taios pure p-nuclei s+p s+r 176174 Hf 176 Hf 176177 Hf 176178 Hf 176179 Hf 176180 Hf p s s+r s+rs+r s+r 3 176175 HfLu 176 HfLu 10 s+r s t-190 W-180 Hg-196 176168 HfYb 176170 HfYb 176171 HfYb 176172 HfYb 176173 HfYb 176174 HfYb 176 HfYb Se-74 Kr-78 Sr-84 Mo-94 Ru-98 Pd-102 Cd-106 Sn-114 Te-120 Xe-126 Ba-132 Gd-152 Dy-158 Er-164 Yb-168 Hf-174 Os-184 P p s s+r s+r s+r s+r Ce-138 r 10 2 176169 HfTm In-113 s+r 176166 HfEr 176167 HfEr 176168 HfEr 176170 HfEr 10 1 s+r s+r s+r r post r-process s-process N(s)/N(p) 40 1 20 0 30 40 50 60 70 The ratios are almost 10 -1 30 40 50 60 70 80 constant over a wide Atomic Number Z range of atomic numnber. Empirical scaling and Universality of gamma-process 1. We found an empirical scaling law that N(s)/N(p) ratios are almost constant over a wide range of atomic number at the solar system. 2. This indicates that the p-nuclei are produced from seed s-nuclei by successive photodisintegration reactions as (gamma, n) reactions. 3. This is a piece of evidence that the most probable origin of the p-nuclei is supernova gamma-process. 4. The fact that the scaling is observed at the solar abundances indicates a novel concept of the universality of gamma-process that the scaling holds for nuclei produced by individual gamma-processes under various astrophysical conditions. T. Hayakawa et al., Phys. Rev. Lett. 93, 161102, (2004). Calculated results under various conditions by N.Iwamoto (JAEA) O/Ne layer in Type II Supernovae s-processed solar abundances 25 M 、 1 Z 、 1foe 40 M 、 1 Z 、 1foe 25 M 、 1 Z 、 20 foe 25 M 、 0.05 Z 、 1foe The ratios under various conditions are constant over a wide range of the atomic number, respectively. Why is the scaling independent of the supernova conditions ? Three mechanisms contribute to this universality. T.Hayakawa et al., Astrophys. J. 648, L47, (2006). 1st mechanism: Effect of the weak s- process Weak s-process change the initial abundances of seed elements of A>90 to that of the AGB star s-process. The seed abundances at individual SNe are almost identical. Weak s-process Massive Stars Neutron0 irradiations AGB stars Interstellar Medium x 1000 Contamination from -2 early genaration stars r-process peak s-Process r-process peak Weak s-Process -4 r-process hill Mass Distribution of s-Nuclei s-Nuclei -6 -8 Log (Mass Fraction) -10 Heavy Elements p-Nuclei Solar System -12 Supernova Explosions γ -Process 100 150 200 Open: Initial seed Mass Number A Closed: Seed after the weak s-process 2nd mechanism: The shift of γ-process layers Peak Temperatures T9 T9 Explosion Energy: 1ｘ1051 erg Explosion Energy: 20ｘ1051 erg 3.5 3.5 1.7 1.7 Mass Mass 2.0 2.8 2.8 4.6 The mass regions of the γ-process layers shift depending the energy and mass to keep their peak temperature. Arnould76, Woosley78,Rayet90 Inside the gamma-process layers, all the seed nuclei are destoryed. Outside the gamma-process layers, the p-nuclei cannot be produced because of their low temperature. The physical conditions at individual SNe are almost identical. 3rd mechanism: effect of two reaction paths The p-nuclei are synthesized by TWO nucleosynthesis paths. 1. Direct (gamma, n) reactions from the heavy isotopes (the first path). 2. Beta decay from neutron-deficient nuclei after the freezeout. Second path flow at the freezeout 102 Se Sr Mo Pd Sn Xe Ce Dy Yb W Pt Kr Ru Cd Te Ba Gd Er Hf Os Hg In Hf 101 Lu N(s)/N(p) 1 168 180 Yb p s (a) 10-1 Tm 169 100 (b) 162 164 166 167 168 Er p p s 80 Ho 165 60 156 158 160 Dy p p s 161 162 163 164 40 20 909192 93 94 95 96 97 98 99 100 Percentage (%) N = 50 N = 82 0 A schematic flow 30 40 50 60 70 80 Atomic Number Z 1. The percentage of the 1st path is dominant in the mass region of N < 82. 2. The second path may contribute in the mass region of N > 82, but its effect is small since both the p- and s-nuclei are populated. Extended scaling There are pairs of 2nd p-nucleus and s-nucleus. Circles: N(s)/N(1st p) ratios Triangles: N(s)/N(2nd p) ratios Corrected observed scaling 169Tm p+s s+r 164Er 166Er 167Er 168Er 163Ho 164Ho 165Ho post r-procrss 162Dy 163Dy 164Dy 166Er is not shielded against the beta-decay and has a contamination of the r-process. •We corrected the contamination of the s-process for Gd and r-process for Ce,Er, W. Most ratios are centered around 23 within a factor of 2. •The three deviations for Ce,Er, W are a piece of evidence that the weak s-process occur before the supernova explosions. Calculated ratio and input nuclear data The p-nuclei are synthesized by the TWO nucleosynthesis paths. Second path flow at the freezeout Hf Lu 168 180 Yb p s Tm 169 162 164 166 Er p p s 167 168 Ho 165 156 158 160 Dy p p s 161 162 163 164 909192 93 94 95 96 97 98 99 100 A schematic flow In a case of Dy, only the s-nucleus 160Dy is populated by beta-decay and thereby the s/p ratio increases, while, in Er, only the p-nucleus 164Er is populated and the s/p ratio decreases. The calculated ratios are sensitive to (gamma,alpha) reaction rates ! Solar Abundances The abundanes of s-nuclei are almost constant in each mass region. The pattern of the p-nuclei is similar to that of the s-nuclei. Summary • We find the two empirical scaling laws for the p- and s-nuclei in the solar system abundance, which is evidence that the most probable origin of the p-nuclei is photodisintegration reactions in SNe. • This leads to a novel concept "The universality of the γ-process". T. Hayakawa et al., Phys. Rev. Lett. 93, 161102, (2004). • The universality originate from the three mechanisms: the weak s-process, the layer shift to keep the peak temperature, the contribution of beta decay. T.Hayakawa et al., Astrophys. J. 648, L47, (2006). • The scaling is extended for N(s)/N(1st p) and N(s)/N(2nd p) and the contributions of other processes are corrected. • There are a piece of evidence of the weak s-process associated with SNe. •The calculated ratios are sensitive to (gamma,alpha) reaction rates. T.Hayakawa et al., to be submitted..
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