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Nuclear Structure 2016 July 29, 2016

Electron-capture Rates at Stellar Environments and Nucleosynthesis Toshio Suzuki Nihon University, Tokyo. Nuclear Structure 2016 July 29, 2016. 1. GT strengths in pf-shell nuclei with GXPF1J and evaluation of e-capture rates at stellar environments

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Nuclear Structure 2016 July 29, 2016

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  1. Electron-capture Rates at Stellar Environments and NucleosynthesisToshio Suzuki Nihon University, Tokyo Nuclear Structure 2016 July 29, 2016

  2. 1. GT strengths in pf-shell nuclei with GXPF1J and evaluation of e-capture rates at stellar environments 2. Nucleosynthesis of iron-group nuclei in type Ia supernova explosions (SNe) 3. Capture rates in pf-g shell nuclei (78Ni) importantfor nucleosynthesis in core-collapse SNe 4. Weak rates in sd-shell nuclei and nuclear URCA processes in stars with O-Ne-Mg core

  3. 1. GT strengts in pf-shell and e-capture rates at stellar environmemts GXPF1:Honma et al., PR C65 (2002); C69 (2004); A=47-66 KB3: Caurier et al., Rev. Mod. Phys. 77, 427 (2005) KB3G A = 47-52 KB + monopole corrections ・ Spin properties of fp-shell nuclei are well described 8-13MeV M1 strength(GXPF1J) gAeff/gAfree=0.74 B(GT-) for 58Ni gSeff/gS=0.75±0.2 Fujita et al.

  4. B(GT+) and e-capture rates for 58Ni and 60Ni Electron-capture rates Ye = No. electrons/No. baryons Exp: Hagemann et al., PL B579 (2004) Exp: Anantaraman et al., PR C78 (2008) Suzuki, Honma, Mao, Otsuka, Kajino, PR C83, 044619 (2011) Comparison of e-capture rates: KB3G vs GXPF1A vs RPA Cole et al., PR C86, 015809 (2012)

  5. GT strength in 56Ni: GXPF1J vs KB3G vs KBF KBF: Table by Langanke and Martinez-Pinedo, At. Data and Nucle. Data Tables 79, 1 (2001) ・fp-shell nuclei: KBF Caurier et al., NP A653, 439 (1999) ・Experimental data available are taken into account: Experimantal Q-values, energies and B(GT) values available ・Densities and temperatures at FFN (Fuller-Fowler-Newton)grids: (p,n) Sasano et al PRL 107 (2011)

  6. 2. Type-Ia SNe and synthesis of iron-group nuclei Accretion of matter to white-dwarf from binary star → supernova explosion when white-dwarf mass ≈ Chandrasekhar limit → 56Ni (N=Z) → 56Ni (e-, ν)56Co Ye =0.5 →　Ye < 0.5 (neutron-rich) → production of neutron-rich isotopes; more 58Ni Decrease of e-capture rate on 56Ni → less production of 58Ni. NSE(Nuclear Statistical Equilibrium) calculation GXPF1 -> 58Ni/56Ni decreases Ye Famiano e-capture rates: GXPF1J < KB3G ←→　Ye (GXPF1J) > Ye (KB3G) t (s)

  7. Problem of over-production of neutron-excess isotopes such as 58Ni, 54Cr … compared with solar abundances Iwamoto et al., ApJ. Suppl, 125, 439 (1999) e-capture rates with FFN (Fuller-Fowler-Newton) Type-Ia SNeW7 model： fast deflagration 58Ni 54Cr Initial: C-O white dwarf, M=1.0M☉ central; ρ9=2.12, Tc=1x107K 54Fe 56Fe cf. WS15-DD1 Slow deflagration + delayed detonation Right figure: Time dependence of density and temperature for different mass zones T t ρ

  8. e-capture rates: GXP; GXPF1J (21≤Z≤32) and KBF (other Z) GXP:W7(fast deflagration) GXP W7 56Ni W7 54Fe 58Ni 54Cr GXP: WDD2 (slow deflagration + detonation) 54Cr 58Ni 54Fe 32S 36Ar 40Ca 28Si

  9. GXP vs KBF GXP/KBF W7 Ye W7 Z GXP≿KBF N GXP/KBF WDD2 GXP/KBF W7 GXP/KBF cf. Langanke and Martinez-Pinedo, RMP 75, 819 (2003)

  10. 3. Weak rates of pf-g shell nuclei and core-collapse SNe Approx. SM SMMC+RPA Sullivan et al., ApJ. 816, 44 (2016)

  11. Which nuclei affect Ÿe (change of Ye) most in core-collapse process? 78Ni ・Approx. rates of Sullivan et al. ・RPA ・SM (pf-g9/2d5/2; modified A3DA) Q= -18.88 MeV (set to be HFB21’s) gAeff/gA=0.74 (1.0) for GT (other multipoles) RPA (SGII) RPA≈Sullivan

  12. Effects of truncation of space pf-gds is enough, pf-g9/2d5/2 is not enough RPA(pf-g9/2d5/2)≈SM(pf-g9/2d5/2) SM: modified A3DA; pf-g9/2d5/2 Y.Tsunoda et al., PRC 89, 031301R (2014) Ex(2+) = 2.8 MeV Up to 5p-5h outside filling config.of 78Ni SM with pf-gds in progress 58Ni→58Cu SM cf. Maduruga

  13. Hybrid model : SM + RPA Effects of gAeff SM(0-,1+,2-;pf-g9/2d5/2)+ RPA (other multipoles) 〜 RPA gAeff/gA = 0.74 in all multipoles vs. gAeff/gA = 0.74 in GT only ・Q-values (calculated values) FRDM: -21.19 MeV RPA(HFB21): -18.88 RPA (SGII): -16.29 SM (A3DA: 5p-5h): -18.1 (-27.426 MeV without Coulomb correction; Δ EC=7.86+1.5 ≈9.36)

  14. 4. Nuclear URCA processes in O-Ne-Mg cores (sd-shell) C burning in 8-10 M☉ stars → O-Ne-Mg core Cooling of O-Ne-Mg core in 8-10 M☉ starsby URCA processes e-capture: β-decay: They occur simultaneously at certain stellar conditions and energy is lost from stars by emissions of ν and → Cooling of stars How much star is cooled → fate of the star afterneon flash: → EC-SNe or CC-SNe Q value is small for A=23, 25, 27 pairs ・Βeta-decay Q-values

  15. 　・Nuclear weak rates in sd-shell (1) New shell-model Hamiltonian: USDB (2) Fine meshes in both density and temperature (Δlog10(ρYe)=0.02,Δ log10T=0.05) cf. Interpolation problem in FFN grids FFN grids are rather scarce, especially for the density (3) Effects of screening: reduce (enhance) e-capture (β-decay) rates Suzuki, Toki and Nomoto, ApJ. 817, 163 (2016) (23Ne, 23Na) (25Na, 25Mg) URCA density at URCA density at log10ρYe= 8.92 log10ρYe= 8.78

  16. Cooling of O-Ne-Mg core by the nuclear URCA processes Fate of 8-10M☉ stars CC-SN A=25 A=23 EC-SN WD 8.8M☉ star collapses triggered by subsequent e-capture on 24Mg and 20Ne (e-capture supernova explosion) Border of CC-SN or EC-SN is at M〜9M☉, which is quite sensitive to nuclear weak rates Toki, Suzuki, Nomoto, Jones and Hirschi, PR C 88, 015806 (2013) Jones et al., Astrophys. J. 772, 150 (2013)

  17. Coulomb corrections: screening effects • Screening effects of electrons V (r) with screening effects of relativistic degenerate electronliquid Juodagalvis et al., Nucl. Phys. A 848, 454(2010). Itoh et al, Astrophys. J. 579, 380 (2002). Vs(0)>0 → reduce (enhance) e-capure (β-decay) rates 2. Change of threshold energy μC(Z) =the correction of the chemical potential of the ion with Z Z-1 Z μc(Z)<0 ΔQc→ reduce e-capture rates & enhance β-decay rates Slattery, Doolen, DeWitt, Phys. Rev. A26, 2255 (1982). Ichimaru, Rev. Mod. Phys. 65, 255 (1993). ρYe= 8.78→ 8.81 URCA density → higher density region

  18. Summary A new shell model Hamiltonian GXPF1J well describes the spin responses in pf-shell nuclei . GT strengths in Ni and Fe isotopes, which are generally more spread compared to KB3G and KBF, are consistent with recent experimental data, especially in 56Ni. ・ Electron capture rates in Ni isotopes (56Ni etc.), iron-group nuclei and pf-shell nuclei are evaluated with GXPF1J at stellar environments, and applied to nucleosynthesis in Type Ia SNe. ・ GXPF1J gives smaller e-capture rates compared with KB3G, KBF and FFN, and leads to larger Ye with less neutron-rich isotopes, and thus can solve the over-production problem in iron-group nuclei. ・ e-capture rates for 78Ni are evaluated by RPA and SM (pf-g9/2d5/2) RPA ≈ Sullivan’s formula (gAeff /gA for SD transitions =1.0) SM: need for extension to fp-gds configurations; in progress Precise evaluation of Q value is important.

  19. ・Detailed e-capture and beta-decay rates for URCA nuclear pairs in 8-10 solar-mass stars are evaluated. → Nuclear URCA process for A=25 and 23 pairs are important for the cooling of O-Ne-Mg core, and determine the fate of stars with ～9M☉whether they end up with e-capture SNe or core-collapse SNe. Precise evaluation of nuclear weak rates is essential. Toki, Suzuki, Nomoto, Jones and Hirschi, PR C 88, 015806 (2013) Jones et al., Astrophys. J. 772, 150 (2013) Suzuki, Toki, and Nomoto, ApJ. 817, 163 (2016)

  20. Collaborators M. Honmaa, K. Morib, M. Famianoc, T. Kajinob,d, N. Shimizue, Y. Tsunodae, T. Otsukaf, K. Nomotog, H. Tokih, S. Jonesi, R. Hirschij, J. Hidakak, K. Iwamotol aUniversity of Aizu bNational Astronomical Observatory of Japan cWestern Michigan University dDepartment of Astronomy, the University of Tokyo eCNS, the University of Tokyo fDepartment of Physics, the University of Tokyo gWPI, the University of Tokyo hRCNP, Osaka University i Heidelberg University jKeele University kMeisei University lDepartment of Physics, Nihon University

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