INT Workshop: The r-process: status and challenges July 28 - August 1, 2014 Nucleosynthesis of heavy elements: r-process and its astrophysical site Cas A (Chandra X-Ray observatory) Rezzolla et al. Almudena Arcones Helmholtz Young Investigator Group INT Workshop: The r-process: status and challenges July 28 - August 1, 2014 Nucleosynthesis of heavy elements: r-processes and their astrophysical sites Cas A (Chandra X-Ray observatory) Rezzolla et al. Almudena Arcones Helmholtz Young Investigator Group s-process uranium r-process masses measured Big Bang: H, He at the ESR iron peak 82 neutron capture burning r-process in stellar interiors path 126 gold stable nuclei 50 r-processwill be measured 82 with CR at FAIR s-process silver 28 nuclides with 50 Z 20 known masses 8 28 Nuclear processes and 20 8 N solar abundances r-process Rapid neutron capture compared to beta decay 27 20 -3 Neutron density: Nn ~ 10 - 10 cm Temperature: T ~ 1010 - 108 K Protons Beta decay (n → p + e number neutron Magic - + ν Neutron capture e) Stable nuclei nuclei in lab r-process path Neutrons Magic neutron number neutron Magic Where does the r-process occur? rapid process ➞ explosions high neutron densities ➞ neutron stars Core-collapse supernovae Neutron star mergers Neutron stars Cas A (Chandra X-Ray observatory) Neutron-star merger simulation (S. Rosswog) core-collapse supernovae r-process in core-collapse supernovae? (B2FH 1957) • prompt explosion (Hillebrandt 1978, Hillebrandt et al. 1984) • neutrino-driven wind (Meyer et al. 1992, Woosley et al. 1994) • shocked surface layers (Ning, Qian, Meyer 2007) • neutrino-induced in He shells (Banerjee, Haxton, Qian 2011) • jets (e.g., Winteler et al. 2012) wind Core-collapse supernova: ONeMg - ONeMg core: Pe reduced as e captured collapse (electron-capture supernova) Prompt explosion (Hillebrandt 1978, Hillebrandt et al. 1984) not confirmed by modern supernova simulations (Kitaura, Janka, Hillebrandt 2006) Delayed neutrino-driven explosion works for this progenitor even in 1D (Kitaura et al. 2006, Fischer et al. 2010) Prompt explosion excluded as r-process site Core-collapse supernova: ONeMg r-process in the shocked surface layers (Ning, Qian, Meyer 2007): • very high velocity (c/3) • high entropy • slightly neutron rich is sufficient Core-collapse supernova: ONeMg r-process in the shocked surface layers (Ning, Qian, Meyer 2007): not found in • very high velocity (c/3) simulations • high entropy • slightly neutron rich is sufficient Janka et al. 2008, Hoffman et al. 2008, Wanajo et al. 2009 Core-collapse supernova: ONeMg r-process in the shocked surface layers (Ning, Qian, Meyer 2007): not found in • very high velocity (c/3) simulations • high entropy • slightly neutron rich is sufficient Janka et al. 2008, Hoffman et al. 2008, Wanajo et al. 2009 One model for low mass progenitors: 8.8Msun (Nomoto 1984, 1987) Promising scenario for the r-process, requires further investigation Eichler, Arcones, Thielemann 2012 Ye Supernova-jet-like explosion 3D magneto-hydrodynamical simulations: rapid rotation and strong magnetic fields matter collimates: neutron-rich jets right r-process conditions Ye simulation: only ν emission Ye corrected for ν absorption Winteler, Käppeli, Perego et al. 2012 Neutrino-induced r-process in He shell -3 at low metallicity Z<10 Zsun → low seed abundance neutral- and charged-current neutrino reactions on He → few neutrons cold r-process relative low neutron density lasts ~20s peaks shift to high A (between r- and s-process) Banerjee, Haxton, Qian 2011 Epstein, Colgate, Haxton 1988, Woosley, Hartmann, Hoffman, Haxton 1990 Nadyozhin, Panov, Blinnikov 1998 R [km] Initial Phase of Collapse R [km] Neutrino Trapping (t ~ 0) δ (t ~ 0.1s, c ~10¹² g/cm³) R Fe ~ 3000 RFe νe νe νe ~ 100 Si Si ν e Fe, Ni Fe, Ni νe νe M(r) [M ] M(r) [M ] 0.5 1.0 ~ MCh 0.5 Mhc 1.0 heavy nuclei Si−burning shell Si−burning shell R [km] R [km] Shock Propagation and ν e Burst δ Bounce and Shock Formationδ (t ~ 0.11s, c ∼< 2 o) R (t ~ 0.12s) RFe Fe Rs ~ 100 km νe radius of νe shock Rν formation νe position of νe shock ~ 10 Si ν Si e formation ν Fe e Fe, Ni free n, νe p Ni νe M(r) [M ] 0.5 1.0 M(r) [M ] 0.5 1.0 nuclear matter δ nuclearδ matter nuclei nuclei ( ∼> ο) Si−burning shell Neutrino-driven Siwinds−burning shell Shock Stagnation and ν Heating, R [km] R [km] Neutrino Cooling and Neutrino− Explosion (t ~ 0.2s) 5 10 Driven Wind (t ~ 10s) neutrons and protons form α-particles Rs ~ 200 α-particles recombine into seed nuclei 4 ν ,ν νe,µ,τ ,νe,µ,τ 10 e,µ,τ e,µ,τ Ni R ~ 100 3 g free n, p Si 10 Si p R ν ~ 50 2 α He νe 10 n νe,µ,τ ,νe,µ,τ r−process? νe,µ,τ ,νe,µ,τ νe O R ns ~ 10 Rν M(r) [M ] n M(r) [M ] PNS 1.3 gain layer 1.5 PNS 1.4 α,n 9 3 n, p α,n, Be, cooling layer 12 C, seed NSE → charged particle reactions / α-process → r-process Figure 2. Schematic representation of the processes that occur in a c o l l a p s i n g s t e l l a r ir o n c o r e o n t h e w a y t o t h e weak r-process supernova explosion. The diagrams (from top left to bottom right)Tv i s=u a l10ize -th 8e pGKhys i c a l c o n d i t i o n s a t t h e o n s e t8o f- 2 GK νp-process core collapse, neutrino trapping, shock formation, propagation of the prompt shock, shock stagnation and revival by neutrino heating, and r-process nucleosynthesis in the neutrino-driven wind of the newly formed neutron star, T < 3 GK respectively, as suggested by current computer simulations. In the forup ap reviewer par seets o Arconesf the fi &g uThielemannres the d y(2013)namical state is shown, with arrows indicating the flow of the stellar fluid. The lower parts of the figures contain information about the nuclear composition of the stellar plasma and the role of neutrinos during the different phases. 41 Neutrino-driven wind parameters r-process ⇒ high neutron-to-seed ratio (Yn/Yseed~100) - Short expansion time scale: inhibit α-process and formation of seed nuclei - High entropy: photons dissociate seed nuclei into nucleons - Electron fraction: Ye<0.5 Otsuki et al. 2000 Ye=0.45 Neutrino-driven wind parameters r-process ⇒ high neutron-to-seed ratio (Yn/Yseed~100) - Short expansion time scale: inhibit α-process and formation of seed nuclei - High entropy: photons dissociate seed nuclei into nucleons - Electron fraction: Ye<0.5 Otsuki et al. 2000 Conditions are not realized in Ye=0.45 hydrodynamic simulations (Arcones et al. 2007, Fischer et al. 2010, Hüdepohl et al. 2010, Roberts et al. 2010, Arcones & Janka 2011, ...) Swind = 50 - 120 kB/nuc τ = few ms Ye ≈ 0.4 - 0.6? Additional ingredients: wind termination, extra energy source, rotation and magnetic fields, neutrino oscillations neutron-star mergers Rezzolla et al. 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 − − − simulations: 21 mergers of 2 neutron stars 2 of neutron star black hole 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 Neutron star mergers: robust r-process 1.2M 1.4M 1.4M 1.4M 2M 1.4M − − − simulations: 21 mergers of 2 neutron stars 2 of neutron star black hole 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 T (GK) ρ (g cm-3) Korobkin et al. 2012 T (GK) ρ (g cm-3) Korobkin et al. 2012 T (GK) ρ (g cm-3) Korobkin et al. 2012 T (GK) ρ (g cm-3) robust r-process Korobkin et al. 2012 Neutron star mergers: neutrino-driven wind 3D simulations ~100ms after merger Perego et al. (2014) disk and neutrino-wind evolution neutrino emission and absorption Nucleosynthesis for few trajectories see also Just et al. 2014, Sekiguchi et al. Neutron star mergers: evaporation disk 2D simulations with simple neutrino treatment outflows from accretion disk: black hole, super-massive neutron star matter unbound: viscosity and alpha recombination Fernandez & Metzger 2013 see also Just et al. 2014 Neutron star mergers: evaporation disk 2D simulations with simple neutrino treatment outflows from accretion disk: black hole, super-massive neutron star matter unbound: viscosity and alpha recombination Fernandez & Metzger 2013 Metzger & Fernandez 2014 see also Just et al. 2014 Radioactive decay in neutron star mergers r-process heating affects: - merger dynamics: late X-ray emission in short GRBs (Metzger, Arcones, Quataert,Martinez-Pinedo 2010) - remnant evolution (Rosswog, Korobkin, Arcones, Thielemann, Piran 2014) 1 day, heating 1 day, no heating 1 year, heating 1 year, no heating Radioactive decay in neutron star mergers Transient with kilo-nova luminosity (Metzger et al. 2010, Roberts et al. 2011, Goriely et al. 2011): direct observation of r-process, EM counter part to GW Multi messenger (e.g. Metzger & Berger 2012, Rosswog 2012, Bauswein et al.