r-Process nucleosynthesis in neutron star mergers and GW170817
Jonas Lippuner July 18, 2018 FRIB and the GW170817 Kilonova FRIB/NSCL/MSU, East Lansing MI
Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA
Los Alamos National Laboratory UNCLASSIFIED LA-UR-18-21867 Outline
1. r-Process nucleosynthesis overview 2. r-Process in neutron star mergers 3. Observational signature and first detection
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 2 Solar system abundances
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 3 Solar system abundances
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 3 The s-process
slow neutron capture 90Zr 91Zr 92Zr
τ ≪ τ ∼ 2 − 5 89 β− n 10 10 yr Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 4 The s-process
slow neutron capture 90Zr 91Zr 92Zr
τ ≪ τ ∼ 2 − 5 89 β− n 10 10 yr Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 4 The r-process
rapid neutron capture 90Zr 91Zr 92Zr τ ≪ τ ∼ n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 5 The r-process
rapid neutron capture 90Zr 91Zr 92Zr τ ≪ τ ∼ n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 5 Double peaks due to closed neutron shells
τ ≪ τ ∼ 2 − 5 90 91 92 s-process: β− n 10 10 yr Zr Zr Zr τ ≪ τ ∼ r-process: n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 6 Double peaks due to closed neutron shells
τ ≪ τ ∼ 2 − 5 90 91 92 s-process: β− n 10 10 yr Zr Zr Zr τ ≪ τ ∼ r-process: n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 6 Double peaks due to closed neutron shells
τ ≪ τ ∼ 2 − 5 90 91 92 s-process: β− n 10 10 yr Zr Zr Zr τ ≪ τ ∼ r-process: n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 6 Double peaks due to closed neutron shells
τ ≪ τ ∼ 2 − 5 90 91 92 s-process: β− n 10 10 yr Zr Zr Zr τ ≪ τ ∼ r-process: n β− 10 ms – 10 s 89Y
84Sr 86Sr 87Sr 88Sr
85Rb 87Rb
78Kr 80Kr 82Kr 83Kr 84Kr 86Kr
79Br 81Br
74Se 76Se 77Se 78Se 80Se 82Se
75As
70Ge 72Ge 73Ge 74Ge 76Ge
69Ga 71Ga
66Zn 67Zn 68Zn 70Zn
65Cu
neutron drip line closed neutron shell
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 6 Solar system abundances
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 7 SkyNet
Sky Net bitbucket.org/jlippuner/skynet
• General-purpose nuclear reaction network • ∼8000 isotopes, ∼140,000 nuclear reactions • Evolves temperature based on nuclear reactions • Input: ρ(t), initial composition, entropy • Open source
Lippuner, J. and Roberts, L. F., ApJS 233, 18 (2017)
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 8 SkyNet features
Science • Extended Timmes equation of state (EOS) • Calculate nuclear statistical equilibrium (NSE) • NSE evolution mode • Calculate inverse rates from detailed balance to be consistent with NSE • Electron screening with smooth transition between weak and strong screening (reactions and NSE)
Code • Adaptive time stepping • Python bindings • Modularity • Extendible reaction class (currently REACLIB, table, neutrino) • Make movies
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 9 Outline
1. r-Process nucleosynthesis overview 2. r-Process in neutron star mergers 3. Observational signature and first detection
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 10 Merger ejecta: Dynamical
Tidal tails or collision interface −4 −2 NS–NS: Mej ∼ 10 − few × 10 M⊙, Ye ∼ 0.05 − 0.45 −1 NS–BH: Mej ∼ 0 − 10 M⊙, Ye . 0.2
Bauswein+13, Hotokezaka+13, Foucart+14, Sekiguchi+15, Kyutoku+15, Radice+16
From Price+06
From Bauswein+13
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 11 Merger ejecta: Disk outflow
Neutrino driven wind or outflow due to viscous heating and α recombination −3 Mej ∼ few × 10 M⊙, Ye ∼ 0.2 − 0.45
Surman+08, Wanajo+11, Fernandez+13,´ Perego+14, Just+15, Foucart+15
From Perego+14 From Fernandez+13´
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 12 Movie
http://jonaslippuner.com/skynet/SkyNet_Ye_0.010_s_010.000_tau_007.100.mp4 http://jonaslippuner.com/skynet/SkyNet_Ye_0.250_s_010.000_tau_007.100.mp4
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 13 r-Process abundances vs. electron fraction
10−2 = Ye 0.01 Observed solar r-process
Ye = 0.19 10−3 Ye = 0.25
Ye = 0.50 10−4
10−5
Abundance 10−6
10−7
10−8
10−9 0 25 50 75 100 125 150 175 200 225 250 Mass number A JL, Roberts 2015, ApJ 815, 82, arXiv:1508.03133
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 14 Full binary neutron star merger simulations
From Wanajo+14 From Wanajo+14
See also Goriely+15
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 15 Nucleosynthesis in HMNS disk outflow
• 3 M⊙ central HMNS or BH, 0.03 M⊙ accretion disk • Variable HMNS lifetime, neutrino leakage, α viscosity
Figure from Metzger & Fernandez´ (2014)
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 16 Final abundances
10−2 Observed solar r-process
10−3 A
Y 10−4 ej M
10−5
10−6 Final abundance −7 10 τ = 0 ms τ = 100 ms τ = 10 ms τ = 300 ms −8 10 τ = 30 ms τ = ∞
10−9 0 25 50 75 100 125 150 175 200 225 250
Mass number A JL, Fernandez,´ Roberts, et al. 2017, MNRAS 472, 904, arXiv:1703.06216
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 17 Black hole–neutron star merger
Roberts, JL, Duez, et al. 2017, MNRAS 464, 3907, arXiv:1601.07942 1. Full GR simulation of BH–NS Francois Foucart (UNH), Foucart et al., Phys. Rev. D 90, 024026 (2014) 2. Evolve ejecta in SPH code Matt Duez (WSU) 3. Nucleosynthesis with varying neutrino luminosity JL and Luke Roberts (MSU)
Figure credit: F. Foucart
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 18 BHNS: Final abundances vs. neutrino luminosity
10−2
Lνe,52 = 0.2 Lνe,52 = 25
Lνe,52 = 1 Solar r-process 10−3
10−4
10−5
10−6 Relative final abundance
10−7
10−8 0 50 100 150 200 250 Mass number A
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 19 Neutrino driven wind in core-collapse supernovae
• Neutrinos emitted from hot proto-neutron star can drive outflow of n and p • Neutrino driven wind is mildly neutron-rich → r-process?
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 20 Jet in MHD-driven supernova
• Requires very high magnetic field (B ∼ 1012 − 1013 G) and rapid rotation • Maybe 0.1 − 1% of all core-collapse supernovae
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 21 Jet in MHD-driven supernova
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 22 Outline
1. r-Process nucleosynthesis overview 2. r-Process in neutron star mergers 3. Observational signature and first detection
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 23 Observational signature of r-process: Kilonova
Metzger & Berger, 2012, ApJ 746, 48
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 24 Impact of lanthanides
2 = . 10− Ye 0 01 Observed solar r-process Ye = 0.19 Lanthanides = . 10−3 Ye 0 25 Actinides Ye = 0.50
10−4
10−5
Abundance 10−6
10−7
10−8
10−9 0 25 50 75 100 125 150 175 200 225 250 Mass number A
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 25 Impact of lanthanides
1042 −1 = . s = 10 kB baryon Ye 0 01 Ye = 0.19 τ = 7.1 ms Ye = 0.25
] = . = 1 M 0 01 M⊙ Ye 0.50 − Luminosity 1041 Heating rate
1040 Luminosity, heating rate [erg s
1039 0 5 10 15
Time [day]
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 26 First neutron star merger observation: GW170817
LIGO et al. 2017, ApJL 848, L13
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 27 GW170817: Hunt for electromagnetic counterpart
• LIGO/VIRGO localization: 31 deg2 ∼ 150full moons • Distance estimate: 40 ± 8 Mpc • 49 galaxies in that volume • Check all galaxies starting with most massive first
Kasliwal et al., 2017, Science 358, 1559
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 28 GW170817: Counterpart discovered in NGC 4993
• Discovered 10.9 hours after merger • Host galaxy: NGC 4993, elliptical galaxy, constellation Hydra, 40 Mpc ∼ 130 Mly
Credit: 1M2H Team / UC Santa Cruz & Carnegie Observatories / Ryan Foley
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 29 GW170817: Rapid color evolution
Credit: ESO / N.R. Tanvir, A.J. Levan and the VIN-ROUGE collaboration
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 30 GW170817: Huge observing campaign
LIGO et al., 2017, ApJL 848, L12
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 31 GW170817: Combined light curve
Villar et al., 2017, ApJL 851, L21
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 32 GW170817: One-component kilonova models fail
Cowperthwaite et al., 2017, ApJL 848, L17
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 33 GW170817: Two-component models do better
Tanvir et al., 2017, ApJL 848, L27 Troja et al., 2017, Nature 551, 71
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 34 GW170817: Three-component model needed?
Villar et al., 2017, ApJL 851, L21
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 35 GW170817: Featureless optical spectrum
Nicholl et al., 2017, ApJL 848, L18
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 36 GW170817: Infrared spectrum
Chornock et al., 2017, ApJL 848, L19
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 37 GW170817: What we learned
• Confirmed neutron star mergers make short GRBs (but this was a weird GRB) −2 • Total ejecta mass larger than expected: ∼ 5 × 10 M⊙ • Neutron star mergers can easily make all r-process material in the galaxy • Blue (lanthanide-free) component larger than expected, maybe large disk wind or blue dynamical component • Lanthanide-rich component is evidence for full r-process, tens of Earth masses of gold and platinum −3 −2 2 −1 • “Purple” kilonova component with XLa ∼ 10 − 10 , κ ∼ 3 cm g ? • Gravity propagates at the speed of light, rules out many alternative theories of gravity besides Einstein’s General Relativity
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 38 Summary
• s- and r-process create heavy elements beyond the iron peak • r-process happens in dynamical and disk ejecta in a neutron star merger • Dynamical ejecta (NS-NS and BH-NS) is generally neutron-rich enough for full r-process • Neutron star mergers are probably the dominant site of the r-process, core-collapse supernovae may contribute weakly • GW170817: First LIGO detection of neutron star merger accompanied by GRB and kilonova – Kilonova followed pretty well what we expected – Yet more work is needed to understand light curve in detail, purple component?
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 39 Extra slides
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 40 Solar system abundances
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 41 First (wrong) attempt: αβγ
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 42 Birth of modern theory of nucleosynthesis: B2FH
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 43 SkyNet
Define abundance
ni Yi = . (1) nB Consider reaction
p + 7Li → 2 4He (2)
with rate λ = λ(T ,ρ). Then ˙ Y4He = 2λYpY7Li + · · · , ˙ Yp = −λYpY7Li + · · · , ˙ Y7Li = −λYpY7Li + · · · (3) Need to solve big, stiff, non-linear system of ODEs
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 44 NS–NS ejecta sources: Tidal tails
Ye ∼ 0.05 − 0.45
Credit: D. J. Price et al. (2006)
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 45 NS–NS ejecta sources: Collision interface
Ye ∼ 0.05 − 0.45
Credit: D. Berry, SkyWorks Digital, Inc.
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 46 NS–NS ejecta sources: Disk outflow
Ye ∼ 0.2 − 0.45
Credit: A. Bauswein et al. (2013)
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 47 Parametrized r-process
Lippuner & Roberts, 2015, ApJ, 815, 82, arXiv:1508.03133 Parameters
0.01 ≤ Ye ≤ 0.50 initialelectronfraction −1 −1 1 kB baryon ≤ s ≤ 100 kB baryon initial specific entropy 0.1 ms ≤ τ ≤ 500ms expansiontimescale
Density profile 1 0
−t/τ −3 ρ0e t ≤ 3τ ρ/ρ 10 τ t 3 3 ρ( ,τ)= 3τ −6 ρ0 t ≥ 3τ 10 = te t Density 10−9 10−3 10−2 10−1 1 101 102 103 Time t/τ Initial conditions
• Choose initial temperature T0 = 6 GK
• Find ρ0 by solving for NSE at T0 and Ye that produces specified s
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 48 Final abundances vs. entropy
10−2 s = 1 kB Observed solar r-process s = 3.2 kB 10−3 s = 10 kB s = 100 kB 10−4
10−5
Abundance 10−6
10−7
10−8
10−9 0 25 50 75 100 125 150 175 200 225 250 Mass number A JL, Roberts 2015, ApJ 815, 82, arXiv:1508.03133
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 49 Electron fraction distribution
2.25 τ = 0 ms 2.00 τ = 10 ms τ = 30 ms 1.75 τ = 100 ms τ = 300 ms 1.50 τ = ∞ ] ⊙ M
3 1.25 −
1.00
Mass [10 0.75
0.50
0.25
0.00 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55
Electron fraction Ye
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 50 Ejected mass
30 Ye ≤ 0.25 Ye > 0.25 25 ] ⊙
M 20 3 −
15
10 Ejected mass [10
5
0 0 10 30 100 300 ∞ HMNS lifetime [ms]
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 51 BHNS: Electron fraction distribution
0.08
Lνe,52 = 0.2 L = 1 0.07 νe,52 Lνe,52 = 25
0.06
0.05 ] ⊙ M 0.04 Mass [ 0.03
0.02
0.01
0.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30
Electron fraction Ye
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 52 Light curves vs. electron fraction 0 1042
Lanthanide and actinide mass fraction XLa+Ac Peak time tp [day] Peak effective temperature T [K] 5 eff . −1 −1 4 Peak Luminosity [erg s ] 41
− 10 −1 s = 10 kB baryon 3000 / −2 τ = 1 ms eff T 40 5, 10 −
3 6000K
/ −3 p t
, 6 days
La+Ac 39
X 10 −4 log 1600K 1 day
−5 1038 0.0 0.1 0.2 0.3 0.4 0.5
Los Alamos National Laboratory ElectronUNCLASSIFIED fraction Ye 3/19/2018 | 53 Recent evidence for rare r-process
• Reticulum II: 1 in 10 highly r-process enhanced ultra-faint dwarf galaxy • Recently discovered second UFD with r-process star: Tucana III Hansen et al., 2017, ApJ 838, 1
Ji et al., 2016, Nature 531, 610
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 54 Recent evidence for rare r-process
244 • Pu is actinide (r-process only) with τ1/2 ∼ 80 Myr (<τmix ∼ 300 Myr) • Interstellar material is swept up and deposited in deep-sea crust • Measure abundance of 244Pu in 25 Myr old deep-sea crust → 244Pu abundance in ISM
From Wallner+15 From Hotokezaka+15
Los Alamos National Laboratory UNCLASSIFIED 3/19/2018 | 55