r-Process nucleosynthesis in neutron star mergers and GW170817 - - PowerPoint PPT Presentation

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r-Process nucleosynthesis in neutron star mergers and GW170817 - - PowerPoint PPT Presentation

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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 Energys NNSA

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Operated by Los Alamos National Security, LLC for the U.S. Department of Energy’s NNSA

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

Los Alamos National Laboratory UNCLASSIFIED LA-UR-18-21867

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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

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Solar system abundances

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Solar system abundances

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The s-process

slow neutron capture τβ− ≪ τn ∼ 102 − 105 yr

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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The s-process

slow neutron capture τβ− ≪ τn ∼ 102 − 105 yr

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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The r-process

rapid neutron capture τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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The r-process

rapid neutron capture τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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Double peaks due to closed neutron shells

s-process: τβ− ≪ τn ∼ 102 − 105 yr r-process: τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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Double peaks due to closed neutron shells

s-process: τβ− ≪ τn ∼ 102 − 105 yr r-process: τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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Double peaks due to closed neutron shells

s-process: τβ− ≪ τn ∼ 102 − 105 yr r-process: τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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Double peaks due to closed neutron shells

s-process: τβ− ≪ τn ∼ 102 − 105 yr r-process: τn ≪ τβ− ∼ 10 ms – 10 s neutron drip line

65Cu 66Zn 67Zn 68Zn 70Zn 69Ga 71Ga 70Ge 72Ge 73Ge 74Ge 76Ge 75As 74Se 76Se 77Se 78Se 80Se 82Se 79Br 81Br 78Kr 80Kr 82Kr 83Kr 84Kr 86Kr 85Rb 87Rb 84Sr 86Sr 87Sr 88Sr 89Y 90Zr 91Zr 92Zr

closed neutron shell

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Solar system abundances

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SkyNet

Sky

Net

b i t b u c k e t . o r g / j l i p p u n e r / s k y n e t

  • 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)

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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

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Outline

  • 1. r-Process nucleosynthesis overview
  • 2. r-Process in neutron star mergers
  • 3. Observational signature and first detection

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Merger ejecta: Dynamical

Tidal tails or collision interface NS–NS: Mej ∼ 10−4 − few × 10−2 M⊙, Ye ∼ 0.05 − 0.45 NS–BH: Mej ∼ 0 − 10−1 M⊙, Ye 0.2

Bauswein+13, Hotokezaka+13, Foucart+14, Sekiguchi+15, Kyutoku+15, Radice+16

From Price+06 From Bauswein+13

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Merger ejecta: Disk outflow

Neutrino driven wind or outflow due to viscous heating and α recombination Mej ∼ few × 10−3 M⊙, Ye ∼ 0.2 − 0.45

Surman+08, Wanajo+11, Fern´ andez+13, Perego+14, Just+15, Foucart+15

From Perego+14 From Fern´ andez+13

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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

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r-Process abundances vs. electron fraction

Observed solar r-process Abundance Mass number A Ye = 0.01 Ye = 0.19 Ye = 0.25 Ye = 0.50 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 25 50 75 100 125 150 175 200 225 250 JL, Roberts 2015, ApJ 815, 82, arXiv:1508.03133

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Full binary neutron star merger simulations

From Wanajo+14 From Wanajo+14 See also Goriely+15

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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 & Fern´ andez (2014)

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Final abundances

Observed solar r-process Final abundance MejYA Mass number A τ = 0 ms τ = 10 ms τ = 30 ms τ = 100 ms τ = 300 ms τ = ∞ 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 25 50 75 100 125 150 175 200 225 250 JL, Fern´ andez, Roberts, et al. 2017, MNRAS 472, 904, arXiv:1703.06216

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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

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BHNS: Final abundances vs. neutrino luminosity

Relative final abundance Mass number A Lνe,52 = 0.2 Lνe,52 = 1 Lνe,52 = 25 Solar r-process 10−8 10−7 10−6 10−5 10−4 10−3 10−2 50 100 150 200 250

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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?

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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

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Jet in MHD-driven supernova

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Outline

  • 1. r-Process nucleosynthesis overview
  • 2. r-Process in neutron star mergers
  • 3. Observational signature and first detection

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Observational signature of r-process: Kilonova

Metzger & Berger, 2012, ApJ 746, 48

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Impact of lanthanides

Abundance Mass number A Observed solar r-process Lanthanides Actinides 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 25 50 75 100 125 150 175 200 225 250 Abundance Mass number A Ye = 0.01 Ye = 0.19 Ye = 0.25 Ye = 0.50 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 25 50 75 100 125 150 175 200 225 250

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Impact of lanthanides

s = 10 kB baryon−1 τ = 7.1 ms M = 0.01 M⊙ Luminosity, heating rate [erg s−1] Time [day] Ye = 0.01 Ye = 0.19 Ye = 0.25 Ye = 0.50 Luminosity Heating rate 1039 1040 1041 1042 5 10 15

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First neutron star merger observation: GW170817

LIGO et al. 2017, ApJL 848, L13

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GW170817: Hunt for electromagnetic counterpart

  • LIGO/VIRGO localization: 31 deg2

∼ 150 full 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

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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

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GW170817: Rapid color evolution

Credit: ESO / N.R. Tanvir, A.J. Levan and the VIN-ROUGE collaboration

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GW170817: Huge observing campaign

LIGO et al., 2017, ApJL 848, L12

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GW170817: Combined light curve

Villar et al., 2017, ApJL 851, L21

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GW170817: One-component kilonova models fail

Cowperthwaite et al., 2017, ApJL 848, L17

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GW170817: Two-component models do better

Troja et al., 2017, Nature 551, 71 Tanvir et al., 2017, ApJL 848, L27

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GW170817: Three-component model needed?

Villar et al., 2017, ApJL 851, L21

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GW170817: Featureless optical spectrum

Nicholl et al., 2017, ApJL 848, L18

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GW170817: Infrared spectrum

Chornock et al., 2017, ApJL 848, L19

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GW170817: What we learned

  • Confirmed neutron star mergers make short GRBs (but this was a weird GRB)
  • Total ejecta mass larger than expected: ∼ 5 × 10−2 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
  • r blue dynamical component
  • Lanthanide-rich component is evidence for full r-process, tens of Earth masses
  • f gold and platinum
  • “Purple” kilonova component with XLa ∼ 10−3 − 10−2, κ ∼ 3 cm2 g−1?
  • Gravity propagates at the speed of light, rules out many alternative theories of

gravity besides Einstein’s General Relativity

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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?

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Extra slides

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Solar system abundances

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First (wrong) attempt: αβγ

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Birth of modern theory of nucleosynthesis: B2FH

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SkyNet

Define abundance Yi = ni nB . (1) 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

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NS–NS ejecta sources: Tidal tails Ye ∼ 0.05 − 0.45

Credit: D. J. Price et al. (2006)

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NS–NS ejecta sources: Collision interface Ye ∼ 0.05 − 0.45

Credit: D. Berry, SkyWorks Digital, Inc.

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NS–NS ejecta sources: Disk outflow Ye ∼ 0.2 − 0.45

Credit: A. Bauswein et al. (2013)

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Parametrized r-process

Lippuner & Roberts, 2015, ApJ, 815, 82, arXiv:1508.03133 Parameters 0.01 ≤ Ye ≤ 0.50 initial electron fraction 1 kB baryon−1 ≤ s ≤ 100 kB baryon−1 initial specific entropy 0.1 ms ≤ τ ≤ 500 ms expansion time scale Density profile ρ(t, τ) =    ρ0e−t/τ t ≤ 3τ ρ0 3τ te 3 t ≥ 3τ

t = 3τ Density ρ/ρ0 Time t/τ 10−9 10−6 10−3 1 10−3 10−2 10−1 1 101 102 103

Initial conditions

  • Choose initial temperature T0 = 6 GK
  • Find ρ0 by solving for NSE at T0 and Ye that produces specified s

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Final abundances vs. entropy

Observed solar r-process Abundance Mass number A skB = 1 skB = 3.2 skB = 10 skB = 100 10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2 25 50 75 100 125 150 175 200 225 250 JL, Roberts 2015, ApJ 815, 82, arXiv:1508.03133

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Electron fraction distribution

Mass [10−3 M⊙] Electron fraction Ye τ = 0 ms τ = 10 ms τ = 30 ms τ = 100 ms τ = 300 ms τ = ∞ 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55

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Ejected mass

Ejected mass [10−3 M⊙] HMNS lifetime [ms] Ye ≤ 0.25 Ye > 0.25 5 10 15 20 25 30 10 30 100 300 ∞

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BHNS: Electron fraction distribution

Mass [M⊙] Electron fraction Ye Lνe,52 = 0.2 Lνe,52 = 1 Lνe,52 = 25 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.00 0.05 0.10 0.15 0.20 0.25 0.30

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Light curves vs. electron fraction

s = 10 kB baryon−1 τ = 1 ms 6 days 1 day 1600 K 6000 K log XLa+Ac, tp/3 − 5, Teff/3000 − 4.5 Electron fraction Ye Lanthanide and actinide mass fraction XLa+Ac Peak time tp [day] Peak effective temperature Teff [K] Peak Luminosity [erg s−1] −5 −4 −3 −2 −1 0.0 0.1 0.2 0.3 0.4 0.5 1038 1039 1040 1041 1042

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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

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Recent evidence for rare r-process

  • 244Pu 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

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