Nucleosynthesis of heavy elements in supernovae and neutron-star mergers Almudena Arcones The very metal-deficient star Oldest observed stars HE 0107-5240 Silver Eu Gold Elemental abundances in: - ultra metal-poor stars and - solar system ‣Robust r-process for 56<Z<83 ‣Scatter for lighter heavy elements, Z~40 How many “r-processes” contribute to solar system and UMP stars abundances? Sneden, Cowan, Gallino 2008 The r-process: what do we know? • Solar system: residual r-process r-process peaks and path → fast neutron capture • Astrophysical environment: explosive and high neutron density • UMP stars: robust process from 2nd to 3rd peak contribution from other process(es) below 2nd peak • Chemical evolution: r-process does not occur in every core-collapse supernovae The r-process: what do we know? • Solar system: residual r-process r-process peaks and path → fast neutron capture • Astrophysical environment: explosive and high neutron density • UMP stars: robust process from 2nd to 3rd peak contribution from other process(es) below 2nd peak • Chemical evolution: r-process does not occur in every core-collapse supernovae What do we need to know better? • Astrophysical site(s) • Nuclear physics Where does the r-process occur? Core-collapse supernovae Neutron star mergers Neutron stars Cas A (Chandra X-Ray observatory) Neutron-star merger simulation (S. Rosswog) •neutrino-driven winds (Woosley et al. 1994,…) •dynamic ejecta •jets (Winteler et al. 2012) •neutrino-driven winds •evaporation disk •shocked surface layers (Ning, Qian, Meyer 2007) •neutrino-induced in He shell (Banerjee, Haxton, Qian 2011) (Lattimer & Schramm 1974, Freiburghaus et al. 1999, ....) Neutrino-driven winds neutrons and protons form α-particles α-particles recombine into seed nuclei NSE → charged particle reactions / α-process → r-process weak r-process T = 10 - 8 GK 8 - 2 GK νp-process T < 3 GK for a review see Arcones & Thielemann (2013) Which elements are produced in neutrino winds? Arcones et al 2007 ❒ mass element Radius [cm] Shock Reverse shock Neutron star time [s] Which elements are produced in neutrino winds? Arcones et al 2007 Silver no r-process ❒ mass element Radius [cm] Shock Reverse shock Neutron star time [s] Lighter heavy elements in neutrino-driven winds νp-process weak r-process proton rich neutron rich observations Honda et al. 2006 Observation pattern reproduced! Overproduction at A=90, magic neutron number N=50 (Hoffman et al. 1996) suggests: Production of p-nuclei only a fraction of neutron-rich ejecta (Wanajo et al. 2011) Arcones & Montes (2011) C.J. Hansen, Montes, Arcones (2014) Lighter heavy elements in neutrino-driven winds νp-process weak r-process proton rich neutron rich observations Sr Sr 5 Overproduction at A=90, magic neutron1 0Observation.66 pattern reproduced! − 0.49 − 0.65 6 − 0number.48 N=50 (Hoffman et al. 1996) suggests:2 0.64 7 − 0Production.63 of p-nuclei − 0only.47 a fraction of neutron-rich ejecta 0.62 8 3 − (Wanajo et al. 2011) − 0.61 9 0.46 0.60 − 4 10 0.45 − Ye 0.59 Ye 0.58 (Arcones &− Montes, 2011) 11 0.44 5 0.57 − − 0.56 12 0.43 6 0.55 − − 0.54 13 0.42 − 7 0.53 14 0.41 − 0.52 − 0.51 15 0.40 8 40 50 60 70 80 90 100 110 − 40 50 60 70 80 90 100 110 − Entropy [kB/nuc] Entropy [kB/nuc] Arcones & Bliss (2014) Lighter heavy elements: Sr - Ag Ultra metal-poor stars with high and low enrichment of heavy r-process nuclei suggest: at least two components or sites (Qian & Wasserburg): Are Honda-like stars the outcome of one nucleosynthesis event or the combination of several? ε ε log log or Z Z Travaglio et al. 2004: solar=r-process+s-process+LEPP Montes et al. 2007: solar LEPP ~ UMP LEPP → unique Nucleosynthesis components Abundance of many UMP stars can be explained by two components: Component abundance pattern: YH and YL Fit abundance as combination of components: Y (Z)=(C Y (Z)+C Y (Z)) 10[Fe/H] calc H H L L · 1 0 L-componentLEPP ∈ -1 H-componentr-process log -2 Fit -3 χ2 = 3.98 0 ∈ BS16089-013 -1 log -2 χ2 = 0.15 -3 35 40 45 50 55 60 65 70 75 Atomic number C.J. Hansen, Montes, Arcones (2014) L-component in neutrino-driven winds observations observations observations Sr/Ag Sr/Zr Observations point to proton-rich conditions Sr/Y Nuclear physics uncertainties? Key reactions: weak r-process 2 10− (α,n) baseline Ye =0.45 3 10− λ 10 for Z =10 30 (α,n) · − 4 λ(α,n) 0.1forZ =10 30 10− · − 5 10− 6 10− abundance 7 10− 8 10− 9 10− baseline Ye =0.45 3 10− λ 10 for Z =30 40 (α,n) · − 4 λ(α,n) 0.1forZ =30 40 10− · − 5 10− 6 10− abundance 7 10− 8 10− 9 10− 10 15 20 25 30 35 40 45 50 55 Bliss, Arcones, Montes, Pereira (in prep.) Z Origin of elements from Sr to Ag Astrophysical site Observations ν wind Chemical evolution [Sr/Fe] Nucleosynthesis: Hansen et al. 2013 identify key reactions [Fe/H] Neutron star mergers Ejecta from three regions: • dynamical ejecta • neutrino-driven wind • disk evaporation disk evaporation Rosswog 2013 Neutron star mergers: robust r-process 1.2M 1.4M 1.4M 1.4M 2M 1.4M − − − Right conditions for a successful r-process (Lattimer & Schramm 1974, Freiburghaus et al. 1999) nucleosynthesis of dynamical ejecta robust r-process: - extreme neutron-rich conditions (Ye =0.04) - several fission cycles Korobkin, Rosswog, Arcones, Winteler (2012) see also Bauswein, Goriely, and Janka Hotokezaka, Kiuchi, Kyutoku, Sekiguchi, Shibata, Tanaka, Wanajo Ramirez-Ruiz, Roberts, ... Neutron star mergers: robust r-process 1.2M 1.4M 1.4M 1.4M 2M 1.4M − − − Right conditions for a successful r-process (Lattimer & Schramm 1974, Freiburghaus et al. 1999) nucleosynthesis of dynamical ejecta robust r-process: - extreme neutron-rich conditions (Ye =0.04) - several fission cycles Korobkin, Rosswog, Arcones, Winteler (2012) see also Bauswein, Goriely, and Janka Hotokezaka, Kiuchi, Kyutoku, Sekiguchi, Shibata, Tanaka, Wanajo Ramirez-Ruiz, Roberts, ... Neutron star mergers: neutrino-driven wind 3D simulations after merger Perego et al. (2014) disk and neutrino-wind evolution neutrino emission and absorption Nucleosynthesis: 17 000 tracers 4 3 2 1 Martin et al. (2015) see also Fernandez & Metzger 2013, Metzger & Fernandez 2014, Just et al. 2014, Sekiguchi et al. Neutron star mergers: neutrino-driven wind Martin et al. (2015) Neutron star mergers: neutrino-driven wind Martin et al. (2015) Time and angle dependency Black hole formation determines time for wind nucleosynthesis (Fernandez & Metzger 2013, Kasen et al. 2015) Early times: low Ye: heavy elements Late times: Ye ~0.35: lighter heavy elements angle dependency Martin et al. (2015) Time and angle dependency Black hole formation determines time for wind nucleosynthesis (Fernandez & Metzger 2013, Kasen et al. 2015) Early times: low Ye: heavy elements Late times: Ye ~0.35: lighter heavy elements angle dependency Martin et al. (2015) Wind and dynamic ejecta Wind ejecta complement dynamic ejecta Complete mixing: solar system abundances and UMP stars dynamical ejecta disk ejecta Martin et al. (2015) Wind and dynamic ejecta Wind ejecta complement dynamic ejecta Complete mixing: solar system abundances and UMP stars Partial mixing: Honda-like star? dynamical ejecta disk ejecta Martin et al. (2015) Nuclear physics input nuclear masses, beta decay, reaction rates (neutron capture), fission Erler et al. (2012) Impact of nuclear masses • Different mass models e.g., Wanajo et al. 2004 Farouqi et al. 2010, Arcones & Martinez-Pinedo 2011 Goriely et al. 2013 Mendoza-Temis et al. 2015 Meng-Ru Wu talk • Sensitivity studies Monte Carlo: all masses ± 1MeV Mumpower, Surman et al. 2015, 2016 Nuclear masses: systematic uncertainty Abundances based on density functional theory - six sets of different parametrisation (Erler et al. 2012) - two realistic astrophysical scenarios: jet-like sn and neutron star mergers Martin, Arcones, Nazarewicz, Olsen (2016) First systematic uncertainty band for r-process abundances Uncertainty band depends on A, in contrast to homogeneous band for all A e.g., Mumpower et al. 2015 Can we link masses to r-process abundances? Two neutron separation energy Nucleosynthesis path at constant Sn: (n,γ)-(γ,n) equilibrium Neutron capture Beta decay S2n/2 = 1.5 MeV Martin, Arcones, Nazarewicz, Olsen (2016) Two neutron separation energy Nucleosynthesis path at constant Sn: (n,γ)-(γ,n) equilibrium Neutron capture Beta decay S2n/2 = 1.5 MeV Martin, Arcones, Nazarewicz, Olsen (2016) Two neutron separation energy: abundances freeze-out abundances before decay Martin, Arcones, Nazarewicz, Olsen (2016) Two neutron separation energy: abundances freeze-out abundances before decay → final abundances neutron capture during decay (Surmann & Engel 2001, Arcones & Martinez-Pinedo 2011) Martin, Arcones, Nazarewicz, Olsen (2016) Two neutron separation energy: abundances freeze-out abundances before decay → final abundances neutron capture during decay (Surmann & Engel 2001, Arcones & Martinez-Pinedo 2011) Martin, Arcones, Nazarewicz, Olsen (2016) Conclusions How many r-processes? How many astrophysical sites? lighter heavy elements (Sr-Y-Zr-...-Ag): neutrino-driven winds heavy r-process: mergers: dynamical, wind, disk evaporation jet-like supernovae Needs Improved supernova and merger simulations: EoS, neutrino rates Neutron-rich nuclei: experiments with radioactive beams, theory Observations: oldest stars, kilo/macronovae, neutrinos, gravitational waves, ... Chemical evolution models .