The r-process and the νp-process Carla Fröhlich Enrico Fermi Fellow The Enrico Fermi Institute University of Chicago GCE April 30 / 2010
Solar System Abundances?? 2 s-process peak r-process peak s-process peak r-process peak s-process peak hydrostatic fusion explosive big bang
Nucleosynthesis Processes Supernovae νp-process Supernovae? 3
The s-, r-, and p-process To explain the abundances of the heavy elements beyond iron Solar abundances (from Anders &Grevesse) s-process r-process p-process 4
The s-process Two sites: 1. He-flashes in ABG stars (strong s-process) 2. Core burning of massive stars (weak s-process) Neutron sources: Secondary process! Depends on seed nuclei from previous generations of nucleosynthesis 1. Protons mixed in from H-shell; 12 C(p,γ) 13 N(β - ) 13 C; 13 C(α,n) 16 O strong neutron source due to full He-abundance in Heburning 2. He-burning: 4 He+ 4 He 8 Be; 8 Be(α,γ) 12 C; 12 C(α,γ) 16 O 14 N(α,γ) 18 F(β + ) 18 O(α,n) 25 Mg C-burning: 12 C( 12 C,α) 20 Ne and 12 C( 12 C,p) 23 Na; 12 C(p,γ) 13 N(β - ) 13 C(α,n) 16 O 5
Neutron-capture Cross Sections Need cross sections with uncertainties between 1 and 5% for complete set of isotopes from 12 C to 210 Po, including unstable samples (branching points) Käppeler et al (2007) N_TOF (CERN) & FRANZ (Frankfurt) 6
The p-process Suggested by Arnould (1976) and Woosley&Howard (1978) Photodisintegrations of pre-existing heavy (s-proces) nuclei In thermal bath of supernova explosions in explosive Ne/O burning layers with peak temperatures of 2-3 10 9 K r s r s 7
Nuclear physics for the p-process Rauscher (2006) 8
Comparison with solar p-only nuclei Arnould & Goriely (2003) Rapp et al (2006) Dillmann et al (2008) 9
The r-process 10
Working of the r-process 1. (very) high entropy α-rich (charged-particle) freeze-out Quasi-equilibria in isotopic chains (chemical equilibrium for neutron captures and photodisintegrations) with maxima at specific neutron separation energies Sn Neutron/seed(A=80) ratio and Sn of r-process path dependent on entropy and e Many parameter studies: Meyer, howard, Takahashi, Hoffman, Qian, Woosley, Freiburghaus, Thielemann, Mathews, Kajino, Wanajo, Otsuki, Terasawa, Farouqi, Goriely, Arcones, Panov, Petermann, ) 2. Low entropies and normal freeze-out with very low e From expanding neutron star-like matter leading also to large n/seed ratios Sn function of e Freiburghaus, Rosswog, Thielemann, Panov, Goriely, Janka 11
The Site(s?) of the r-process Neutrino-driven wind (SNe II) Problems: high enough entropy attained??, neutrino properties??? Neutronstar mergers Problems: ejection too late in galactic evolution He-shells of SNe Credit: S. Rosswog Low-mass (prompt explosion) SNe Credit: H.-T. Janka 12
Core Collapse Simulations with ν-wind General relativistic radiation hydrodynamics with threeflavor neutrino transport in spherical symmetry 10Msun 18Msun formation of ν-driven wind ~1s post-bounce Fischer et al 13 (2009)
Observational Constraints on r-process Sites Apparently uniform abundances above Z=56 (and up to Z=82?) unique astrophysical event which nevertheless consists of a superposition of ejected mass zones Rare event which must be related to massive stars due to early appearance at low metallicities (behaves similar to SN II products like O but with much larger scatter) 14
Core Collapse Supernovae Credit: Thielemann 15
Effect of Neutrino Interactions Multigroup explosions: altering e in the fully dissociated phase Liebendörfer et al (2001) Frohlich et al (2006) If the neutrino flux is sufficient (scales 1/r 2 ): High density / low temperature high E F for electrons e-captures dominate n-rich If electron degeneracy lifted for high T ν e -captures dominate due to n-p mass difference, p-rich composition In late phases when protoneutron star neutron rich, antineutrinos see smaller opacity higher luminosity, dominate in neutrino wind neutron-rich ejecta e>0.5 is generic results of simulations with elaborate ν-transport 16
Effect of Neutrino Interactions Multigroup explosions: altering e in the fully dissociated phase Liebendörfer et al (2001) Frohlich et al (2006) Buras et al (2006) Rampp & Janka (2000) e>0.5 is generic results of simulations with elaborate ν-transport 17
The νp-process proton-rich matter is ejected under the influence of neutrino interactions Nuclei form at distances where a substantial antineutrino flux is present true rp-process is limited by slow β decays, e.g. τ(64ge) Antineutrinos help bridging long waiting points via (n,p) reactions: With neutrinos o Without neutrinos Fröhlich et al 2006 18
19 19 50 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 51 52 53 52 Te 106 Te 107 Te 108 Te 109 Te 110 Te 111 Te 112 51 Sb 103 Sb 104 Sb 105 Sb 106 Sb 107 Sb 108 Sb 109 Sb 110 Sb 111 50 Sn 100 Sn 101 Sn 102 Sn 103 Sn 104 Sn 105 Sn 106 Sn 107 Sn 108 Sn 109 Sn 110 49 In 98 In 99 In 100 In 101 In 102 In 103 In 104 In 105 In 106 In 107 In 108 In 109 48 Cd 97 Cd 98 Cd 99 Cd 100 Cd 101 Cd 102 Cd 103 Cd 104 Cd 105 Cd 106 Cd 107 Cd 108 47 94 95 96 97 98 99 100 101 102 103 104 105 106 107 46 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 45 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 44 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 43 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 42 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 41 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 40 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 39 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 38 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 37 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 Te 105 93 85 83 81 78 79 76 77 72 73 N = Z 54 55 56 59 60 58 67 Z = 50 N = 50 I 109 I 110 I 111 I 112 I 113 I 108 Xe 110 Xe 111 Xe 112 Xe 113 Xe 114 νp process SHIPTRAP REFERENCE NUCLIDES JFLTRAP (adapted from C. Weber) Penning Trap Mass Measurements CANADIAN TRAP at Argonne NL
Effect of New Mass Measurements Same hydrodynamic profile Only reaction rates are different 88 20 This work: Weber et al (2008) [31]: Kankainen et al (2006)
Effect of variations in (n,p) rates 21
Observations Need additional (primary) process for early,, before onset of s-process LEPP Large variations in between different lowmetallicity stars 22
re observations Heavy r-process and Fegroup uncorrelated Ge member of Fe group intermediate behavior, weak correlations with Fegroup as well the heavy elements 23
Summary Explanation of solar system abundances above Fe is more complicated than originally envisioned (s-, r-, and p-process) p-process, light p-nuclei problem; an other process needed (νp-process) S-process: at least two versions (weak and main); results depend on mass and metallicity of stars; solar pattern is integrated feature over galactic evolution R-process: at least two versions (weak and main/strong); speculations on site, especially for the strong r-process. 24
Summary Explanation of solar system abundances above Fe is more complicated than originally envisioned (s-, r-, and p-process) Complexities can only be understood on the basis of firm and solid understanding of nuclear properties Penning traps, radioactive ion beams facilities like NSCL (MSU), ATLAS (ANL), frib (upcoming) Larger telescopes like GMT; surveys see talks day 1 25