Nuclear Astrophysics: The origin of heavy elements Lecture 3: The r process

Gabriel Martínez Pinedo

Isolde lectures on nuclear astrophysics May 9–11, 2017 Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Outline

1 Signatures of heavy element nucleosynthesis

2 Nucleosynthesis in core-collapse supernovae

3 Nucleosynthesis in neutron star mergers Dynamical ejecta Accretion disk ejecta

4 Summary Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Nucleosynthesis beyond iron

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: low neutron densities, nn = 10 cm , τn > τβ (site: intermediate mass stars) 20 −3 r process: large neutron densities, nn > 10 cm , τn  τβ (unknown astrophysical site) p process: photodissociation of s-process material. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Time evolution: metalicity

[Fe/H] ~ -5

[Fe/H] ~ -3

Astronomers use the metalicity: ! ! NFe NFe [Fe/H] = log10 − log10 NH ∗ NH as a proxy for age. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Evolution metalicity Sneden, Cowan & Gallino 2008 a 1.5

1.0 Core-collapse Supernovae Type Ia 0.5 [Mg/Fe] 0

– 0.5

b 1.5

1.0

0.5 [Eu/Fe] 0

– 0.5

–3 –2 –1 0 [Fe/H]

r process occurs already at early galactic history Large scatter at low metalicities: r process is related to rare events not correlated with iron. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary 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 > 50, −2 consistent with solar r-process abundance. −4 Abundances are the result of events that do Relative log not produce iron. [Qian & Wasserburg, Phys. −6 Rept. 442, 237 (2007)]

−8 30 40 50 60 70 80 90 Atomic Number 0.5 (b) Sr 0 Zr translated pattern of CS 22892-052 (Sneden et al. 2003) Ru -0.5 Mo Pd -1 Stars poor in heavy r-process elements but ) Y Z (

ε -1.5 with large abundances of light r-process Nb log -2 elements (Sr, Y, Zr) Ag -2.5 Production of light and heavy r-process -3 HD 122563 (Honda et al. 2006) Eu

elements is decoupled. -3.5 40 50 60 70 80 Atomic Number (Z) Honda et al, ApJ 643, 1180 (2006) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary r-process astrophysical sites

Core-collapse supernovae Neutron star mergers

Explosion of massive stars Mergers eject around 0.01 M of very (M & 9 M ) neutron rich-material (Ye ∼ 0.01). Similar amount of less neutron-rich matter Site: neutrino-winds from cooling (Y 0.2) ejected from accretion disk. of hot protoneutron star. e & Low frequency, high yield High frequency (∼ 0.3 yr−1), low −4 −5 yield ejecta (10 –10 M ) Observational signature: electromagnetic transient from radioactive decay of Observations: not every r-process nuclei [Kilonova/Macronova, supernovae produces r process Metzger et al (2010)] Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Measurements long-lived radioactive nuclei

Both the 244Pu (τ = 81 Myr) accreted via interstellar particles in the Earth deepsea floor and the Early Solar System abundanced are naturally explained with the low-rate/high-yield astrophysical scenario. [Hotokezaka et al, Nature Physics 11, 1042 (2015)] CC Supernova 10,000 LIGO/Virgo R-element mass ( Macronova 1,000 candidate ) 1 A − Pu ≥ r 90) 100 My (

0 R 10 Compact binary merger

1 Advanced LIGO/ Virgo/KAGRA 0.1 0.0001 0.001 0.01 0.1 1

Mej (Msun) Any astrophysical site should fulfill:

RMej = M(A > 90) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Core-collapse supernovae

H.-Th. Janka, et al, PTEP 01A309 (2012)

               "          
    
       ! 




   

         

The movie of the supernova simulation is available here Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Neutrino-driven winds

Main processes: − νe + n  p + e + ν¯e + p  n + e

Neutrino interactions determine the proton to neutron ratio.

Neutrino cooling and Neutrino-driven wind Condition neutron-rich ejecta: 105   Lν¯e h i hEν¯ i − hEν i > 4∆np − − 1 hEν¯ i − 2∆np e e Lν e ν , ν e 104 e,µ,τ e,µ,τ m in k

R Ni neutron-rich ejecta: r-process 103 Si ฀

He proton-rich ejecta: νp-process 102 νp-process ν , –ν r-process O e,µ,τ e,µ,τ R Nucleosynthesis sensitive to spectral ns ~10 Rν PNS differences between ν and ν¯ 1.4 α, p α, p, nuclei 3 e e M(r) in M n, p α, n α, n, nuclei Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary

Evolution luminosities and Ye

1D Boltzmann transport radiation simulations (artificially induced explosion) for a 11.2 M progenitor based on the DD2 EoS (Stefan Typel and Matthias Hempel).

1052 0.60 0.58 0.56 51 0.54 10 0.52 0.50 0.48 50 Electron fraction 0.46 Luminosity [ergs/s] 10 0 2 4 6 8 10 0 2 4 6 8 10 Time [s] Time [s] 13 100 12 νe 90 11 80 ν¯e /baryon] 70

10 B [MeV]

k 60 i 9 νx

ν 50

E 8 40 h 7 30 6 20 0 2 4 6 8 10 Entropy [ 0 2 4 6 8 10 Time [s] Time [s]

Ye is moderately neutron-rich at early times and later becomes proton-rich. GMP, Fischer, Huther, J. Phys. G 41, 044008 (2014). Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Nucleosynthesis

107 6 10 11.2 105 104 103 102 101 100 1 10− 2 Rel. abundance 10− 3 10− 4 10− 50 60 70 80 90 100 110 Mass number A 2 10− 3 10− HD 122563 4 10− 5 10− 6 10− 7 10− 8 10−

Elemental abundance 9 10− 25 30 35 40 45 50 55 Charge number Z

Elements between Zn and Mo (A ∼ 90) are produced Mainly neutron-deficient isotopes are produced Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Compact binary systems: gravitational waves

Orbital decay Hulse & Taylor binary pulsar Gravitational waves binary black holes merger First detection! 9:50:45 UTC, 14 September 2015

LIGO Hanford signal

LIGO Livingston signal

Abbott et al, PRL 116, 061102 (2016) Weisberg & Huang, ApJ 829, 55 (2016) Compact binary systems exist and eventually merge Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Merger channels and ejection mechanism

In mergers we deal with a variety of initial configurations (netron-star neutron-star vs neutron-star black-hole) with additional variations in the mass-ratio. The evolution after the merger also allows for further variations.

NSNS wind; t~100 ms torus unbinding; dyn. ejecta; t~ 1 ms t ~ 1s

⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒

BH formation ⇒

sGRB ⇒

⇒ ⇒ ⇒ ⇒ ⇒ ⇒

NSBH Rosswog, et al, arXiv:1611.09822 Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Making Gold in Nature: r-process nucleosynthesis

250 Known mass Known half−life r−process waiting point (ETFSI−Q)

100 200 98 96

94

92

90

88 Solar r abundances 86 84 188 190 186 82

80

78 184 180 182 76 178 176 74 164 166 168 170 172 174 150 72 162 70 160 N=184 68 158

66 156 154 64 152 150 62 140 142 144 146 148 1 60 138 134 136 58 130 132 0 128 10 56 54 126 124 10 −1 52 122 The r-process requires the knowledge of 120 50 116 118 10 −2 48 112 114 110 46 −3 108 10 100 106 N=126 44 104 the properties of extremely 100 102 42 10 98 96 40 92 94

38 88 90 86 84 r−process path 36 82 neutron-rich nuclei: 34 80 78 32 74 76

30 72 70 28 66 68 64 26 62 N=82 28 60 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 Nuclear masses. Beta-decay half-lives. Neutron capture rates. Fission rates and yields. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Evolution nucleosynthesis in mergers

528 trajectories r-process stars once electron fermi energy drops below ∼ 10 MeV to allow for beta-decays (ρ ∼ 1011 g cm−3). Important role of nuclear energy production (mainly beta decay). Energy production increases temperature to values that allow for an (n, γ)  (γ, n) equilibrium for most of the trajectories. Systematic uncertainties due to variations of astrophysical conditions and nuclear input

Mendoza-Temis, Wu, Langanke, GMP, Bauswein, Janka, PRC 92, 055805 (2015) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Final abundances different mass models Mendoza-Temis, Wu, Langanke, GMP, Bauswein, Janka, PRC 92, 055805 (2015) FRDM WS3 10-3

10-4

10-5

10-6 abundances at 1 Gyr 10-7

10-8 HFB21 DZ31 10-3

10-4

10-5

10-6 abundances at 1 Gyr 10-7

10-8 120 140 160 180 200 220 240 120 140 160 180 200 220 240 mass number, A mass number, A Robustness astrophysical conditions, strong sensitivity to nuclear physics Second peak (A ∼ 130) sensitive to fission yields. Third peak (A ∼ 195) sensitive to masses (neutron captures) and beta-decay half-lives. Elements lighter than (A ∼ 120) are not produced. Possible contribution of the ejecta from accretion disks. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Temporal evolution (selected phases)

Fission is fundamental to determine the final r-process abundances. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Nuclear physics uncertainties: beta decays

Masses around N ∼ 126 and half-lives for Z & 80 have a strong impact on the position of A ∼ 195 [Eichler et al., ApJ 808, 30 (2015)] Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Merger channels and ejection mechanism

In mergers we deal with a variety of initial configurations (netron-star neutron-star vs neutron-star black-hole) with additional variations in the mass-ratio. The evolution after the merger also allows for further variations.

NSNS wind; t~100 ms torus unbinding; dyn. ejecta; t~ 1 ms t ~ 1s

⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒

BH formation ⇒

sGRB ⇒

⇒ ⇒ ⇒ ⇒ ⇒ ⇒

NSBH Rosswog, et al, arXiv:1611.09822 Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Ejecta from neutron star accretion disks

Perego, et al, MNRAS 443, 3134 (2014)

Contributes mainly to the production of nuclei with A < 120.

Martin, et al, ApJ 813, 2 (2015) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Nucleosynthesis in black-hole accretion disk ejecta

Accretion disk around compact 4 3.5

object is expected to eject M)

-4 3 material with broad Ye 2.5 distribution [Fernández, Metzger, 2 1.5 MNRAS 435, 502 (2013)] 1 0.5

This material is expected to ejecta mass (10 0 contribute to the production of 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Y all r-process nuclides [Wu et al, e,5

MNRAS 463, 2323 (2016)] M) 10-2 10-2 solar r abundance solar r abundance FRDM masses FRDM+QRPA 10-3 DZ31 masses 10-3 D3C*

10-4 10-4

10-5 10-5

10-6 10-6 abundances at 1 Gyr abundances at 1 Gyr

10-7 10-7 0 50 100 150 200 250 300 0 50 100 150 200 250 300 mass number, A mass number, A Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Observational signatures

Inspiral Dynamical Accretion Remnant Short GRB X-ray/radio X-ray extended precursor? ?? emission/plateau Neutron ?? precursor Blue kilonova Red Radio (UV) kilonova transient Coalescence Coalescence GW “chirp” GWs from remnant NS?

r-process Free n? BH Shocked ISM Shocked > 0.25 >

e

ms magnetar? Y Ye < 0.25 ̀ ̀ Event Signal Phase

NS NS

Seconds Milliseconds 10 ms 100 ms Minutes–hours Hours–days Days–weeks Months–years

Fernández and Metzger, Annu. Rev. Nucl. Part. Sci. 66, 23 (2016) Metzger, arXiv:1610.09381 [astro-ph.HE] Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Kilonova/Macronova electromagnetic transient

Electromagnetic transitent from radioactive decay r-process ejecta [Li & Paczy´nski 1998] Luminosities ∼ 1000 times those of a nova [Metzger et al, 2010] Large optical opacities of Lanthanides delay the peak to timescales of a week in the red/infrared [Kasen et al, 2013] Proably observed associated to GRB 130603B

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

23 –12

10 X-ray Dux (erg s

24

5 25 1.6 m

̀ –1 –13 10 cm AB magnitude 26 –2 ) 27

N 28 10–14

29 E 104 105 106 Time since GRB 130603B (s) First direct observation of an r-process event? Tanvir+, Nature 500, 457 (2013) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Actinides affect opacities and energy production

Actinides can be an important opacity source at timescales of weeks. They can substantially contribute to energy production via alpha decay. Mendoza-Temis, Wu, Langanke, GMP, Bauswein, Janka, PRC 92, 055805 (2015) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Impact on the light curve

Light curve contains nuclear physics signatures.

1041

) 40 1 10 − 1039 (ergs s 1038 bol L 1037 FRDM (Beta-decay dominates) DZ31 (Alpha-decay dominates) 1036 0 5 10 15 20 25 30 Days Ratio of luminosities at peak value and at late times can be used to constrain the produced amount of nuclei between Pb and U. Barnes, Kasen, Wu, GMP, ApJ 829, 110 (2016) Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Summary

Heavy element nucleosynthesis in core-collapse supernovae is limited to elements between Zn and Mo (A ∼ 90). Neutron star mergers are likely the site where the “main r process” takes place. The combination of dynamical ejecta and disk outflow ejecta can account for the solar system r-process abundances. Radioactive decay of r-process ejecta produces an electromagnetic transient. Likely observed in GRB 130603B. Further detections necessary to confirm that the r process occurs in mergers. Signatures of heavy element nucleosynthesis Nucleosynthesis in core-collapse supernovae Nucleosynthesis in neutron star mergers Summary Modeling uncertainties

Sekiguchi, et al, PRDM-691, 064059 (2015) 100 SFHo Dynamical ejecta originates DD2 from shock heated regions 10-1 TM1

during the merger. 10-2

-3 Weak processes at high Fraction of mass 10

temperature can affect the 0 0.1 0.2 0.3 0.4 0.5 neutron richness of ejecta: Ye Radice, et al, MNRAS 460 3255 (2016) − e + p  n + νe 100 HY QC + e + n  p + ν¯e LK QC M0 QC 1

ej 10 There is no consensus on the −

impact M/M 2 10− Not important for neutron star

- black hole mergers. 3 10− 0.08 0.16 0.24 0.32 0.40 Ye