Nucleosynthesis of Heavy Elements: R-Process and Its Astrophysical Site

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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 Magic neutron number - + ν Neutron capture e) Stable nuclei

nuclei in lab

r-process path Neutrons Magic neutron number 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 ~ 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 Metzger & Fernandez

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. 2013) 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. 2013)

Berger, Fong & Chornock, 2013 Tanaka & Hotokezaka, 2013, Hotokezaka et al. 2013 Grossman, Korobkin, Rosswog, Piran, 2014 Where does the r-process occur?

Rare core-collapse supernovae Neutron star mergers

Neutron stars

Cas A (Chandra X-Ray observatory) Neutron-star merger simulation (S. Rosswog) Galactic chemical evolution

First stars: H, He Heavy elements New generation of stars

Interstellar medium (ISM)

The very metal-deﬁcient star HE 0107-5240 (Hamburg-ESO survey) Trends with metallicity

core-collapse supernovae Fe and Mg produced in type Ia same site: core-collapse supernovae

Signiﬁcant scatter at low metallicities

r-process production rare in the early Galaxy

Mg and Fe production is not coupled to r-process production

Sneden, Cowan, Gallino 2008 ~time Fingerprint of the r-process

Oldest observed stars Solar system abundances

Silver Eu Gold

Mass number Atomic number

Sneden, Cowan, Gallino 2008 LEPP: Lighter Element Primary Process

Ultra metal-poor stars with high and low enrichment of heavy r-process nuclei suggest: at least two components or sites (Qian & Wasserburg):

LEPP heavy r-process Travaglio et al. 2004: solar=r-process+s-process+LEPP Montes et al. 2007: solar LEPP ~ UMP LEPP → unique

Are Honda-like stars the outcome of one nucleosynthesis event or the combination of several? log ε log ε or

Z Z Nucleosynthesis components

C.J. Hansen, Montes, Arcones 2014

LEPP and r-process components based on 3 methods:

M1: LEPP = Honda star r-process = Sneden star

M2: LEPP = Honda - Sneden r-process = Sneden

M3: iterative method (Li et al. 2013) LEPP = LEPP - r-process r-process = r-process - LEPP

➞ Component abundance pattern: Yr and YL Assumptions: Z range for components robust pattern lines = M1 Abundance deconvolution big sample of stars (Frebel et al. 2010) remove s-process, carbon enhanced, and stars with internal mixing

ﬁt abundance as combination of components: Y (Z)=(C Y (Z)+C Y (Z)) 10[Fe/H] calc r r L L · 1

0 LEPP ∈ -1 r-process log -2 Fit -3 χ2 = 3.98

∈ BS16089-013 -1 log -2 χ2 = 0.15 -3

35 40 45 50 55 60 65 70 75 Atomic number Abundance deconvolution big sample of stars (Frebel et al. 2010) remove s-process, carbon enhanced, and stars with internal mixing

ﬁt abundance as combination of components: Y (Z)=(C Y (Z)+C Y (Z)) 10[Fe/H] calc r r L L · 1

0 LEPP ∈ -1 r-process log -2 Fit -3 χ2 = 3.98

∈ BS16089-013 -1 log -2 χ2 = 0.15 -3

35 40 45 50 55 60 65 70 75 Atomic number Abundance deconvolution big sample of stars (Frebel et al. 2010) remove s-process, carbon enhanced, and stars with internal mixing

ﬁt abundance as combination of components: Y (Z)=(C Y (Z)+C Y (Z)) 10[Fe/H] calc r r L L · 1

0 LEPP ∈ -1 r-process log -2 Fit -3 χ2 = 3.98

∈ BS16089-013 -1 log -2 χ2 = 0.15 -3

35 40 45 50 55 60 65 70 75 Atomic number Abundance deconvolution big sample of stars (Frebel et al. 2010) remove s-process, carbon enhanced, and stars with internal mixing

ﬁt abundance as combination of components: Ycalc(Z)=(CrYr(Z)+CLYL(Z))

0.32 dex one outlier expected (obs. + method) distribution LEPP in neutrino winds?

Arcones et al. 2007

❒ 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

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) Electron capture supernova

Wanajo, Janka, Müller (2011): small neutron-rich pockets in 2D simulations Lighter heavy elements in neutrino-driven winds

νp-process weak r-process

proton rich neutron rich

observations

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) 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) LEPP components: constraining conditions

LEPP abundance ratios: Sr/Y = 6.13 (//) Sr/Zr = 1.22 (\\) Sr/Ag = 48.2 LEPP components: constraining conditions

LEPP abundance ratios: Sr/Y = 6.13 (//) Sr/Zr = 1.22 (\\) Sr/Ag Sr/Zr Sr/Ag = 48.2 Sr/Y Conclusions

How many r-processes? How many astrophysical sites? heavy r-process: mergers: dynamical, wind, disk evaporation jet-like supernovae He shell lighter heavy elements: neutrino-driven winds mergers: wind, disk evaporation constraints from observations: LEPP component Needs Observations: oldest stars, kilo/macronovae, neutrinos, gravitational waves, ...

Neutron-rich nuclei: experiments with radioactive beams, theory

Improved supernova and merger simulations

Chemical evolution models