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Nuclear Physics Phenomena in Cataclysmic Stellar Binary Systems

Nuclear Physics Phenomena in Cataclysmic Stellar Binary Systems. Michael Wiescher (University of Notre Dame). Interplay of Nuclear and Astrophysics Characteristic features of x-ray bursts Ignition (clusterization in nuclei) Time-scale (mass & shape of nuclei)

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Nuclear Physics Phenomena in Cataclysmic Stellar Binary Systems

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  1. Nuclear Physics Phenomena in Cataclysmic Stellar Binary Systems Michael Wiescher (University of Notre Dame) • Interplay of Nuclear and Astrophysics • Characteristic features of x-ray bursts • Ignition (clusterization in nuclei) • Time-scale (mass & shape of nuclei) • Fate of Ashes from Thermo to Pycno (halo of nuclei) APS Meeting, Philadelphia 2003

  2. Nuclear Astrophysics • Nuclear reactions control stellar evolution lifetimes of stellar burning phases • Nuclear reactions control stellar explosion timescale of energy release

  3. 6 4 Flux 2 0 0.7 0.6 Area 0.5 0.4 0.3 12 0 6 2 10 4 8 Time [s] The evolution of a thermonuclear Runaway  x-ray burst Ṁ~10-8 M☉ • Accretion onto neutron star • Ignition at one location • Spread of explosion front • Thermonuclear runaway

  4. T- conditions in accretion layer ⇧⇧⇧ Ejection? Accretion  Accretion  Compression  High T High  Thermo-nuclear reactions Pycno-nuclear reactions

  5. (T1) (E) (T2) E Thermo-nuclear reactions for ideal gas conditions Low energy resonant contributions at stellar energies <2 MeV!

  6.  = 106 g/cm3 105g/cm3 106g/cm3 Sn Pd Mo Sr Waiting Points Se Zn 42 5 ·1038 38 Fe AWmax 4 AWmin 3 Luminosity [erg/s] 2 1 0 200 300 100 Time [s] rp-Process End Point 70 74 66 62 58 54 50 46 34 Ti 30 Ar 26 22 Si 18 Ne 14 C 10 Ignition He 6 2

  7. Alpha Cluster Structure in T=0,1 nuclei Pronounced  clustering in T=0,1 nuclei near  threshold Excitation-Energy Mass-Number

  8. 3-a-Process 7.654 MeV 0+ 0.0 MeV 0+ 7.367 MeV -.092 MeV 4He 8Be • Reaction rates determined by • cluster state configurations providing strong resonances! 12C

  9. Mg 14O+a Ne O 18Ne 16 18 C Be 22Mg 12 14 10 He 2 4 6 8 Break-Out: 14O(a,p), 18Ne(a,p) 14O(a,p)17F(p,g)18Ne(a,p)21Na(p,g)22Mg Near threshold cluster states in: 18Ne, 22Mg,? Alpha cluster configuration near a-threshold in T=1 nuclei causes strong alpha capture resonances & rapid break-out!

  10. Break-Out HCNO O 200 400 600 800 1000 Time [s] Consequences of break-out -cluster configuration near  threshold  enhanced -capture rates  break-out

  11. 67As+p 69Se 72Br 68Se 67As 68As 69Br 74Sr 70Kr 70Br 72Kr 73Rb 74Rb 73Kr 71Br 71Kr 69Br+p b+ 68Se+p 70Kr 68As Waiting point equilibrium

  12. 100 AW Jaenecke 10 P-system 1 Shape isomer FRDM T1/2 [s] 0.1 0.01 Effective half-live of 68Se Ganil 0.001 0.0001 -2 -1 0 1 Q-value [MeV] Nuclear Masses & Nuclear Shape Shape deformations leads to shape isomeric states! Capture on long-lived isomers may increase reaction flow!

  13. is 0+ is 0+ gs 0+ gs 0+ Shape Isomers (Bouchez et al PRL 90l, 2003) New theoretical predictions of shape isomers for A=68,72 N=Z Nuclei using the projected shell model approach. (Yang Sun, 2003)

  14. 64Ge 68Se, 68Se* 56Ni 104Sn 72Kr,72Kr* Abundances Proton capture on shape-isomer states increases the reaction flow and reduces the timescale for rp-process nucleosynthesis during cooling phase.

  15. -2 10 -3 10 Sn -4 10 Pd -5 10 Mo -6 10 Sr 0 20 40 60 80 100 120 mass number Se Zn Fe 74 70 Ti 62 66 56Fe 56Cr 56Sc 56Ti 54 58 Ar 50 Si 46 56Mn 56V 42 38 Ne 34 30 26 22 C 18 He 14 2 10 6 abundance Electron-capture driven conversion from proton-rich to neutron rich (Ouellette, Schatz, Langanke 2003)

  16. S [MeV-b] large Z small rate Pycno-Nuclear Reactions At densities >r=1012g/cm3 nuclei are densely frozen in lattice position. Pycnonuclear reactions occur when the deflecting Coulomb barrier is reduced by close distance and electron cloud between neighbor nuclei. (Salpeter at al, 1956) (Koonin, Schramm 1992)

  17. Pycno-nuclear reactions (Beard, Wiescher 2003)

  18. 1 0.1 0.01 neutron density 16O 24Ne 0.001 20Ne 26O 0.0001 4 0 6 8 12 2 10 radius [fm] Neutron halo for drip-line nuclei halo profile for near drip-line nuclei Relativistic mean field theory extended halo structure may increase fusion S-factorS(E) significantly (Afanasjev 2003 Chamon 2003)

  19. Total reaction path Sn Pd  = 106 g/cm3 105g/cm3 109g/cm3 1012g/cm3 • triple  process • rp-process • electron capture • pycno-nuclear burning Mo Sr Se Zn Fe 74 70 Ti 62 66 54 58 Ar 50 • Rapid energy release by • Thermo-nuclear reactions •  x-ray burst • Steady energy release by Pycno-nuclear reactions  Crust heating Si 46 42 38 Ne 34 30 26 22 C 18 He 14 2 10 6

  20. Conclusion • Nuclear reaction processes provide the engine for stellar evolution and explosion • Nuclear structure provides the clockwork for stellar processes • Nuclear experiments provide an alternative & complementary approach to classical observation

  21. Acknowledgments Anatoli Afanasjev Notre Dame Ani Aprahamian Notre Dame Victoria Barnard U. Surrey, UK Mary Beard U. Surrey, UK Joachim Görres Notre Dame Karlheinz Langanke U. Århús, Danmark Hendrik Schatz NSCL/MSU Yang Sun Notre Dame Friedel Thielemann U. Basel, Switzerland

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