The role of fission in r-process nucleosynthesis

Gabriel Martínez Pinedo

INT Program INT13-3: “Quantitative Large Amplitude Shape Dynamics: fission and heavy ion fusion”

October 4, 2013

Nuclear Astrophysics Virtual Institute Introduction Fission and the r-process Outline

1 Introduction

2 Fission and the r-process Fission barriers Are super-heavy nuclei produced in the r-process? Shell structure super-heavy nuclei Fission yields Introduction Fission and the r-process Signatures and nucleosynthesis processes

Solar system abudances contain signatures of nuclear structure and nuclear stability. They are the result of different nucleosynthesis processes operating in different astrophysical environments and the chemical evolution of the galaxy.

8 4...6 10 y M~10 Mo

dense 6 molecular star formation (~3%) H condensation clouds 1010 He

8 10 O C Ne interstellar 106-1010 y 6 Si S Fe medium 10 stars star M > 0.08 M D Ca Ni o s 104 infall dudustst 2 winds 10 Ge Sr SN explosion Ba mixing B Xe Pb SNR's & ~90% 100 Li Pt hot Be r s bubbles r s Galactic compact Abundance relative to Silicon = 10 −2 remnant 10 SNIa (WD, 0 20 40 60 80 100 120 140 160 180 200 220 halo 2 6 Mass Number 10 -10 y NS,BH) Introduction Fission and the r-process Nucleosynthesis beyond iron (Traditional description)

Three processes contribute to the nucleosynthesis beyond iron: s-process, r-process and p-process (γ-process).

10 2

80 1 10 s r s ] 0 70 p-drip 6 10 r 10 -1 60 -2 Z 10 50 10 -3 115 Sn 180 p n-drip -4 138 W 40 10 La Abundances [Si=10 152 10 -5 Gd 30 164 180 m Ta 10 -6 Er 40 60 80 100 120 80 100 120 140 160 180 200 N A

10−12 −3 s-process: relatively low neutron densities, nn = 10 cm , τn > τβ 20 −3 r-process: large neutron densities, nn > 10 cm , τn < τβ. p-process: photodissociation of s-process material. Introduction Fission and the r-process Heavy elements and metal-poor stars Cowan & Sneden, Nature 440, 1151 (2006) Stars rich in heavy r-process elements (Z > 50)

0 and poor in iron (r-II stars, [Eu/Fe] > 1.0).

ε Robust abundance patter for Z > 52, −2 consistent with solar r-process abundance. −4 These abundances seem the result of events Relative log that do not produce iron. [Qian & Wasserburg, −6 Phys. Rept. 442, 237 (2007)]

−8 30 40 50 60 70 80 90 Possible Astrophysical Scenario: Neutron star Atomic Number mergers. 0.5 (b) Sr 0 Zr translated pattern of CS 22892-052 (Sneden et al. 2003) Ru Stars poor in heavy r-process elements but -0.5 Mo Pd -1 with large abundances of light r-process ) Y Z ( elements (Sr, Y, Zr) ε -1.5 Nb log -2 Production of light and heavy r-process Ag elements is decoupled. -2.5 -3 HD 122563 (Honda et al. 2006) Eu

Astrophysical scenario: neutrino-driven -3.5 40 50 60 70 80 winds from core-collapse supernova Atomic Number (Z) Honda et al, ApJ 643, 1180 (2006) Introduction Fission and the r-process Astrophysical sites

Core-collapse supernova Neutron star mergers

Neutrino-winds from protoneutron Matter ejected (∼ 0.01 M ) stars. dynamically during merger. Aspherical explosions, Jets, Electromagnetic emission from the Magnetorotational Supernova, ... decay of r-process nuclei [Kilonova, [Winteler et al, ApJ 750, L22 (2012)] Metzger et al, MNRAS 406, 2650 (2010)] Winds from accretion disks around black holes [Wanajo & Janka, ApJ 746, 180 (2012)] Introduction Fission and the r-process Transients from r-process ejecta Introduction Fission and the r-process Radioactive heating and light curve

The r-process heating at late times 1020

−1.3 )

goes like t . −1 56 18 Ni g 10 Fission −1 Beta decay 16 Similar to nuclear waste from 10 Total heating

terrestrial reactors. 1014 Independent of the ejecta 1012 composition. 1010 108 Energy generation (erg s Independent of the nuclear mass 10−6 10−5 10−4 10−3 10−2 10−1 100 101 102 103 model. Time (days) 1042 Light curve reaches peak ) brightness at times of 1 day, −1 reaching luminosities 1000 times 1041 those of a typical Nova.

Results are sensitive to photon Luminosity (erg s Efficiency = 1.0 Efficiency = 0.5 opacities (Kasen et al, 2013) 1040 0.1 1 10 Metzger, GMP, Darbha, Quataert, Arcones et Time (days) al, MNRAS 406, 2650 (2010) Introduction Fission and the r-process Kilonova Observation

LETTER doi:10.1038/nature12505

A ‘kilonova’ associated with the short-duration c-ray burst GRB 130603B

N. R. Tanvir1, A. J. Levan2, A. S. Fruchter3, J. Hjorth4, R. A. Hounsell3, K. Wiersema1 & R. L. Tunnicliffe2

Time since GRB 130603B (d) N 1 10 0.6 m I μ 10–11 21 X-ray F606W F 22 F160W

23 –12 T 10 X-ray Dux (er 24

O5″ 25 g s –1 1.6 μm –13 10 cm AB magnitude 26 –2 N ) 27

N 28 F10–14

29

E 104 105 O106 Time since GRBOO 130603B (s) Direct observation of an r-process nucleosynthesis event?

Nbur Introduction Fission and the r-process Magnetorotationally Driven Supernovae

Winteller et al, ApJ 750, L22 (2012)

] 120 ⊙ M

5 100 − 0 80 [1 ss

a 60 M

d 40 e t

ec 20 j E 0 0.10 0.15 0.20 0.25 0.30 0.35 0.40 Ye

2 10−

] 3 ⊙ 10− [M 4 ss 10− a M 5 d 10− e t ec j 10 6

E −

10 7 − 60 80 100 120 140 160 180 200 220 240 Mass Number Introduction Fission and the r-process Neutron-star mergers: Astrophysically robust

Korobkin, Rosswog, Arcones, & Winteler, MNRAS 426, 1940 (2012)

0.5 Yi Ye -4 0.4 10 0.2

-5 0.3 10 0.1

10-6 0.2 0 13 14 10 10 ns1.0-ns1.0 ns1.4-ns1.4 ejecta mass fraction 3 -7 0.1 l [g/cm ] 10 ns1.2-ns1.2 ns1.2-ns1.0 ns1.4-ns1.0 -8 ns1.4-bh5 0 10 ns1.4-bh10 0 0.05 0.1 0.15 0.2 0.25 0.3 120 130 140 150 160 170 180 190 200 210 Ye Mass number A Introduction Fission and the r-process Sensitive to nuclear physics input

10−3

10−4

10−5

10−6 Abundance Solar r−process Abundances FRDM −7 WS3 10 HFB 21 DZ31 10−8 100 120 140 160 180 200 Mass Number Bauswein, Goriely, Janka, ApJ 773, 78 (2013) Joel Mendoza-Temis (PhD)

Strong sensitivity nuclear physics input and particularly fission. Introduction Fission and the r-process Nuclear physics needs

Fission rates and distributions: • n-induced • spontaneous E-delayed n-emission • E-delayed branchings (final abundances)

E-decay half-lives (abundance and process speed) n-capture rates • for A>130 in slow freezeout • for A<130 maybe in a “weak” r-process ?

Q-physics ? Seed production rates (DDD,DDn, D2n, ..) Masses (Sn) (location of the path) figure from H. Schatz Introduction Fission and the r-process Fission input in the r-process

R-process simulations require rates for neutron capture, beta-decay (including delayed neutron emission) and alpha-decay. Whenever fission becomes important we also need fission rates and yields (including neutrons produced) for the following fission induced reactions: Neutron induced fission Beta-delayed fission Spontaneous fission Gamma induced fission(?) Neutrino induced fission(?) Introduction Fission and the r-process Fission relevance for the r-process

In my opinion these are the questions we need to address: Where in the (Z, N) plane does fission occur at the different phases of the r-process? Does fission constitute a barrier to the production of heavier nuclei or just a “mine field” that can be partly crossed? What are the fission yields produced by the fissioning nuclei? Are there new magic neutron numbers above N = 126? If so, what is their strength? Can long live superheavy nuclei be produced in the r-process? Introduction Fission and the r-process Nuclear Landscape

Erler et al., Nature 486, 509 (2012) 120 Stable nuclei line Known nuclei drip Drip line oton Two-pr N = 258 S Z on drip line 2n = 2 MeV = 82

Z 80

, wo-neutr SV-min T N = 184 110 Z = 50 oton number

Pr 40 N = 126 100 Z = 28 Z N = 82 = 20 90 230 244 N 232 240 248 256 N = 28 = 50 N = 20 0 0 40 80 120 160 200 240 280 Neutron number, N Petermann et al., Eur. Phys. J. A 48, 122 (2012)
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The r-process explores the limits of stability. Fission Barrier Calculations for the r-process nuclei

Full symbols – experimental data Lines – calculations (LDM,TF, ETFSI)

A. Mamdouh et al. NPA679 (2001), 337 Po ETFSI U ETFSI

[MeV] TF

f B TF

LDM LDM Slide from A. Andreyev Slide from

Neutron Number Neutron Number

• Good agreement between Bf,cal and Bf,exp for nuclei close to stability • Large disagreement far of stability (both on n-def. and n-rich sides)1 • Need measured fission data far of stability to ‘tune’ fission models Introduction Fission and the r-process Evolution fission rates

100 0 2 102 10 Beta delayed fission 10 Beta delayed fission 1 101 Neutron induced fission 10 10−1 Neutron induced fission −1 10 Spontaneous fission 100 Spontaneous fission 100 n/seed n/seed −1 −2 −1 −2 10

10 10 ) 10

) −2 −1 −2 10 d −1 s 10 d s ee −3 ( −3 −3 s ee ( e 10 10

10 −3 / t s e 10 / t n a n a −4

−4 R 10 R 10 −4 10−4 10 −5 10−5 10 −6 −6 10 −5 10 10−5 10 −7 10−7 10 −6 −8 10−6 10−8 10 10 0.1 1 10 100 0.1 1 10 100 Time (s) Time (s)

0 10 0 2 2 10 10 10 Beta delayed fission Beta delayed fission 1 101 10 10−1 Neutron induced fission −1 Neutron induced fission 10 Spontaneous fission 100 Spontaneous fission 100 n/seed n/seed −1 −2 −1 −2 10

10 10 ) 10 ) −2 −1 −2 10 d −1 s 10 d s ee −3 ( −3 −3 ee ( s 10 −3 e 10 10 / t s e 10 / t n a n a −4

−4 R 10 R 10 −4 10−4 10 −5 10−5 10 −6 −6 10 −5 10 10−5 10 −7 10−7 10 −6 −8 10−6 10−8 10 10 0.1 1 10 100 0.1 1 10 100 Time (s) Time (s) Fig. 9. The evolution of fission rates for the different channels Fig. 10. Similar to fig. 9, the evolution of fission rates for shown for a hot (top) and cold (bottom) r-process with the the different channels shown for a hot (top) and cold (bottom) fission barrier/mass model selection TF/FRDM. r-process, but with the fission barrier/mass model selection ETFSI/ETFSI.

From Petermann et al., Eur. Phys. J. A 48, 122 (2012) Introduction Fission and the r-process Fission in the r-process

Depends of the fission barriers. It is necessary to consider all fission inducing processes (neutron induced, beta delayed, spontaneous fission, ...) and the corresponding yields. Thomas-Fermi Extended Thomas-Fermi [Myers & Swia¸tecki,´ PRC 60, 014606 (1999)] [Mamdouh et al, NPA 679, 337 (2001)]

•2 0 2 4 6 8 10 •2 0 2 4 6 8 10

120 5 120 1 3 2 7 65432 0 115 2 115 8 8 9 4 6 110 6 0 8 110 0 3 7 6 5 105 5 105 2 1 4 2 Z Z 2 3 2 8 100 3 100 2 4 4 1 4 95 5 3 95 8 4 10 6 6 5 90 7 90 8 6 9 10 7 7 85 85

140 150 160 170 180 190 200 210 220 230 140 150 160 170 180 190 200 210 220 230 N N Neutron-induced fission is the dominating process. Introduction Fission and the r-process Fission in the r-process

Depends of the fission barriers. It is necessary to consider all fission inducing processes (neutron induced, beta delayed, spontaneous fission, ...) and the corresponding yields. Barrier minus neutron separation energy Barrier minus neutron separation energy (TF barriers, FRDM masses). (ETFSI barriers and masses)

•10 •5 0 5 10 •10 •5 0 5 10

120 120

•2 2 115 115 2 6 110 110 0 •2 •2 105 105 •2 •2 Z Z 0 100 100 2 4 2 0 4 95 2 95 0 6 8 6 4 10 90 90 810

85 85

140 150 160 170 180 190 200 210 220 230 140 150 160 170 180 190 200 210 220 230 N N Neutron-induced fission is the dominating process. Introduction Fission and the r-process Neutron-induced fission rates

10 10 JENDL-3.3 JENDL-3.3 ETFSI 1 ETFSI 235 TF 1 JENDL-3.3 TF U(n,f) HFB-14 ETFSI HFB-14 exp 0.1 exp B TF Bf 10 f HFB-14 Panov et al. 2005 0.1 exp 0.01 Panov et al. 2005 Bf Panov et al. 2005 0.001 238 U(n,f) (E) [barn] 0.01 nf

σ 0.0001 236 0.001 U(n,f) 1e-05 1 1e-06 0.0001 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 10 JENDL-3.3 238 239 Pu(n,f) Pu(n,f) ETFSI TF HFB-14 1 exp 10 Bf Panov et al. 2005 237 Np(n,f) 1

(E) [barn] 0.1 JENDL-3.3 JENDL-3.3 nf

σ ETFSI ETFSI TF TF HFB-14 HFB-14 exp exp Bf Bf 1 0.01 Panov et al. 2005 Panov et al. 2005 0.1 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 10 10 10 JENDL-3.3 ETFSI TF 1 HFB-14 1 exp Bf 240 Panov et al. 2005 0.1 Pu(n,f) JENDL-3.3 1 ETFSI 0.1 TF (E) [barn] f JENDL-3.3 HFB-14 n exp 0.01 σ 0.01 ETFSI Bf TF Panov et al. 2005 242 HFB-14 241 Pu(n,f) exp Pu(n,f) B 0.001 0.001 f Panov et al. 2005 0.1 0.0001 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 E, MeV E, MeV E, MeV

Fig. 1. Present predictions of energy-dependent (n, f ) cross sections σn f (E) for some target nuclei of U, Np and Pu calculated in the framework of exp different mass and fission barrier predictions (ETFSI, TF, HFB-14) and experimental data, marked Bf as well. Experimentally measured cross- sections were used after JENDL-3.3 (Nakagawa et al. 2005), averaged by the code JANIS Soppera et al. (2008), displayed by a black line. All the predictions are given for a ground-state population. Our previous results (Panov et al. 2005) are shown as well.

From Panov et al., A&A 513, A61 (2010) Introduction Fission and the r-process Fission in the r-process

Other fission channels become relevant for small neutron densities.

TF barriers ETFSI barriers 115 115 beta delayed fission beta delayed fission 110 spontaneous fission 110 spontaneous fission α decay α decay − − 105 β 105 β

100 100 Z Z 95 95

90 90

85 85

80 80 100 120 140 160 180 200 220 240 100 120 140 160 180 200 220 240 N N Introduction Fission and the r-process Are super-heavy nuclei produced in the r-process?

FRDM masses plus TF barriers ETFSI masses and barriers t = 0.887 s t = 0.7876 s

-4 -4

-6 -6 log Y(A) log Y(A) -8 -8

200 240 280 320 200 240 280 320 A A log Y log Y 0 0

100 -4 100 -4

-8 -8

-12 -12 Z 80 Z 80

-16 -16

-20 -20 60 60

-24 -24 120 140 160 180 200 220 120 140 160 180 200 220 N N Petermann, et al., Eur. Phys. J. A 48, 122 (2012) Introduction Fission and the r-process Are super-heavy nuclei produced in the r-process?

FRDM masses plus TF barriers (t ≈ 10 s) ETFSI masses and barriers t = 10.24 s t = 9.907 s

-4 -4

-6 -6 log Y(A) log Y(A) -8 -8

200 240 280 320 200 240 280 320 A A log Y log Y 0 0

100 -4 100 -4

-8 -8

-12 -12 Z 80 Z 80

-16 -16

-20 -20 60 60

-24 -24 120 140 160 180 200 220 120 140 160 180 200 220 N N Introduction Fission and the r-process Are super-heavy nuclei produced in the r-process?

FRDM masses plus TF barriers (t ≈ 1 h) ETFSI masses and barriers t = 3642 s t = 3849 s

-4 -4

-6 -6 log Y(A) log Y(A) -8 -8

200 240 280 320 200 240 280 320 A A log Y log Y 0 0

100 -4 100 -4

-8 -8

-12 -12 Z 80 Z 80

-16 -16

-20 -20 60 60

-24 -24 120 140 160 180 200 220 120 140 160 180 200 220 N N Introduction Fission and the r-process Are super-heavy nuclei produced in the r-process?

FRDM masses plus TF barriers (t ≈ 10 d) ETFSI masses and barriers t = 9.382e+05 s t = 9.078e+05 s

-4 -4

-6 -6 log Y(A) log Y(A) -8 -8

200 240 280 320 200 240 280 320 A A log Y log Y 0 0

100 -4 100 -4

-8 -8

-12 -12 Z 80 Z 80

-16 -16

-20 -20 60 60

-24 -24 120 140 160 180 200 220 120 140 160 180 200 220 N N Introduction Fission and the r-process Are super-heavy nuclei produced in the r-process?

FRDM masses plus TF barriers (t ≈ 1 yr) ETFSI masses and barriers t = 3.21e+07 s t = 3.307e+07 s

-4 -4

-6 -6 log Y(A) log Y(A) -8 -8

200 240 280 320 200 240 280 320 A A log Y log Y 0 0

100 -4 100 -4

-8 -8

-12 -12 Z 80 Z 80

-16 -16

-20 -20 60 60

-24 -24 120 140 160 180 200 220 120 140 160 180 200 220 N N Introduction Fission and the r-process Influence of shell-structure Hot r-process Cold r-process 10−3 10−3 Z=85 Z=88 Z=88 ETFSI ETFSI Z=85 −4 N=162 N=172 −4 N=172 10 FRDM Z=80 10 FRDM N=162 N=152 Z=80 10−5 10−5 N=150

10−6 10−6

10−7 10−7 Abundance Abundance 10−8 10−8

10−9 −9 n/seed = 1 10 n/seed = 1 10−10 10−10 0 50 100 150 200 250 300 0 50 100 150 200 250 300 Mass number Mass number 20 20 FRDM ETFSI−2 Z = 110 15 15

2n 10 2n 10 S S

5 5

0 0 120 130 140 150 160 170 180 190 200 120 130 140 150 160 170 180 190 200 N N (I. Petermann PhD Thesis) Introduction Fission and the r-process Influence in r-process abundances

Strong N = 184 shell results in larger production of superheavy nuclei. Late time fission produces large changes in the r-process distribution. Hot r-process Cold r-process 10−2 10−2

−3 ETFSI −3 ETFSI 10 FRDM 10 FRDM 10−4 10−4

10−5 10−5

10−6 10−6 Abundance Abundance 10−7 10−7

10−8 Abundances at 1 Gyr 10−8 Abundances at 1 Gyr

10−9 10−9 60 90 120 150 180 210 240 60 90 120 150 180 210 240 Mass number Mass number Introduction Fission and the r-process Role of fission yields

Fission yields are important to determine the final r-process abundance. However, the distribution of produced nuclei is modified by subsequent neutron-captures.

10−1

10−2 ETFSI−Q FRDM 10−3

10−4

−5 Y 10

10−6

10−7

10−8

10−9 60 90 120 150 180 210 240 A

GMP, J. Phys. G 35 014057 (2008). Introduction Fission and the r-process Yields used in r-process calculations

238 282 292 10 U Cm Cf 10

1 (%) A

Y 1 0.1 this work (ABLA code) this work (ABLA code) this work (ABLA code) Nagy et al., 1978 Kodama & Takahashi, 1975 Panov et al., 2008 Panov et al., 2008 Panov et al, 2008 Kodama & Takahashi, 1975 Kodama & Takahashi, 1975 0.01 0.1 80 90 100 110 120 130 140 150 160 120 130 140 150 160 170 120 130 140 150 160 A A A Fig. 10. The final mass distributions of fission fragments for the compound nuclei (after neutron capture) 238U, 282Cm and 292Cf. The distributions were computed with the ABLA code (Kelic´ et al. 2008) as described in the text. In addition, we show the yields computed with the phenomeno- logical parameterizations of Panov et al. (2008) and Kodama & Takahashi (1975), as well as experimental data (crosses).

From Panov et al., A&A 513, A61 (2010) Introduction Fission and the r-process Yields used in r-process calculations

Fission yields for 260Pu:

(a) Panov et al. (2001) (b) Kodama & Takahashi (1975)

(c) Panov et al. (2008) (d) ABLA07

re 2: Comparison of the four di erent ›ssion fragment distribution models on the exam From M. Eichler, et al., Proceedings Nuclear Physics in Astrophysics VI. Introduction Fission and the r-process

10-2 10-2 Panov et al. 2001 Panov et al. 2008 Impact in abundances-3 -3 10 Kodama & Takahashi 1975 10 ABLA07

10-4 10-4 e e c c n n

a -5 -2 a -5-2 d 10 10 d 1100 n n

u Panov et al. 2001 u Panov et al. 2008 b b

a -3 a -3 10-6 10 Kodama & Takahashi 1975 1100-6 ABLA07

-4 -4 10-7 10 1100-7 e e c c n n

a -5 a -5 -8 d 10 d 10-8 10 n 1n 0 u 120 140 160 180 200 u 120 140 160 180 200 b b

a A a A 10-6 10-6

10-7 10-7

10-8 10-8 120 140 160 180 200 120 140 160 180 200 A A

(a) (b)

Figure 3: Final abundances around the second and third peak for a NSM [1] employing four different ›ssion fragment distribution models. For reasons of clarity the results are presented in two graphs. The black dots represent the solar r-process abundances [14]. The mass model is FRDM in all calculations. 10-2 10-2 Panov et al. 2001 Panov et al. 2008 10-3 Kodama & Takahashi 1975 10-3 ABLA07

-4 -4 10 10-2 1100-2 e e c c

n Panov et al. 2001 n Panov et al. 2008

a -5 -3 a -5-3 d 10 10 Kodama & Takahashi 1975 d 1100 ABLA07 n n u u b b

a -4 a -4 10-6 10 1100-6 e e c c n n

a -5 a -5

-7 d 10 d 10-7

10 n 1n 0 u u b b a a 10-6 10-6 10-8 10-8 120 140 160 180 200 120 140 160 180 200 A A 10-7 10-7

10-8 (a) 10-8 (b) 120 140 160 180 200 120 140 160 180 200 A A Figure 4: Same as Figure 3, but for an MHD supernova [2].

From M. Eichler, et al., Proceedings Nuclear Physics in Astrophysics VI. Introduction Fission and the r-process Can fission produce elements lighter than A ∼ 130?

Fission barriers systematics based on Skyrme HF-BCS calculations [Erler, Langanke, Loens, GMP, Reinhard, PRC 85, 025802 (2012)]

120 SLy6 120 HFB14 114 114 108 108 102 102 96 96

proton number 90 proton number 90 84 84

120 SkI3 120 ETFSI 114 114 108 108 102 18 102 18 96 16 96 16

proton number 90 14 proton number 90 14 84 12 84 12 10 10 8 8 120 SV-min 120 FRDM

6 barrier[MeV] 6 barrier[MeV] 114 4 114 4 108 2 108 2 102 102 0 0 96 96

proton number 90 proton number 90 84 84

120 SV-bas 120 TF 114 114 108 108 102 102 96 96

proton number 90 proton number 90 84 84

120 140 160 180 200 220 240 260 120 140 160 180 200 220 240 260 neutron number neutron number

If fission occurs at sufficiently low mass numbers it can produce elements with A < 130.