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报告人：梁帅 指导教师 : 张波 教授

Abundance analysis of s+r stars: r-process abundance comparison between s+r stars and r-rich stars. 报告人：梁帅 指导教师 : 张波 教授. Main Content. 1. Introduction 2. Abundance model for s+r stars 3. Results and Discussion 4. Conclusion. 1. Introduction 1.1 neutron capture process.

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报告人：梁帅 指导教师 : 张波 教授

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  1. Abundance analysis of s+r stars: r-process abundance comparisonbetween s+r stars and r-rich stars 报告人：梁帅 指导教师: 张波 教授

  2. Main Content 1. Introduction 2. Abundance model for s+r stars 3. Results and Discussion 4. Conclusion

  3. 1. Introduction1.1 neutron capture process • Differences between s-process and r-process: sites, neutron density, timescales. • ( Z,A ) +n → (Z,A+1)+γ;(Z,A+1) → (Z+1,A+1) +e • (Z,A)→(Z,A+1)→(Z,A+2)→…→ (Z,A+X)

  4. 1.2 main r-process and weak r-process • main r-process: Z>56 • CS 22892-052, CS 31082-001 • weak r-process: Sr, Y, Zr… • HD 122563, HD 88609

  5. the fitted results for 14 r-rich stars

  6. 1.3 AGB stars and s-process nucleosynthesis • The formation of AGB stars: C-O core, He-shell, H-shell, envelop. • (TP)AGB • Four parameters related to nucleosynthesis △t，nn(107cm-3)，T9(0.1)，r

  7. 1.4 the possible formation scenario of s+r stars • Some stars are observed with carbon and s-element enhanced greatly. • binary system • Companion stars: the former AGB stars, now evolved into white dwarfs. • s+r stars: polluted by both an AGB star and a supernova.

  8. 1.4 the possible formation scenario of s+r stars 1. r-rich ISM and self-pollution 2. Binary system out of r-rich ISM and AGB-pollution 3. Triple system with SN- and AGB-pollution 4. Binary system with AGB- and 1.5 SN-pollution 5. Binary system with AGB- and AIC-pollution 6. Binary system with only AGB-pollution

  9. 2. Abundance model for s+r stars Ni =(CrwNi,rw+CrmNi,rm)10[Fe/H]+ CsANi,sA N i, rw: the abundance produced by the weak r-process. N i, rm : the abundance produced by the main r-process. N i, sA : the abundance produced by the s-process in AGB stars. Crw :the component coeffcient of the weak r-process. Crm : the component coeffcient of the main r-process CsA : the component coeffcient of the s-process

  10. Kfree=5; △τ,0~2mb-1，τ0=-△τ/ln r； r，0~1.

  11. For a better comparison with the component coefficients Crw, Crm, we define a new s-process component coefficient Cs: • CsANBa,sA=CsNBa,s×10[Fe/H] • We choose the solar componet coefficients asa standard and ssume all of them are close to 1.

  12. 3. Results and Discussion3.1 calculated results

  13. 3.2 individual relative offsets and rms offsets

  14. 3.3 Crm,Crwand Csas functionsof [Fe/H] and [Eu/Fe]

  15. 3.4 Fractions vs. [Eu/Fe]

  16. 3.4 Fractions vs. [Eu/Fe]

  17. 3.5 The correlationbetween log Crm and log Cs

  18. 4. Conclusion • 1. The main r-process, weak r-process and s-process abundance pattern adopted in this work is remarkably stable from star to star. • 2. The similar origins of weak r-process material in s+r stars and r-rich stars : they are both formed in the molecular cloud which had been polluted by weak r-process material. • 3. There is a strong correlation between the enhancement of s-process and r-process in s+r stars.

  19. Prospect With the increase of observed abundances for s+r stars, the more information of nucleosynthesis related to s- and r-process can be obtained. It will help us to determine the formation scenario of s+r stars and chemical evolution in the early galaxy.

  20. Looking forward to get your comments. Thank you for your coming!

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