Explosive nucleosynthesis of heavy elements An astrophysical and - - PowerPoint PPT Presentation

Explosive nucleosynthesis of heavy elements

An astrophysical and nuclear physics challenge Gabriel Martínez Pinedo

Nuclear Physics, Compact Stars, and Compact Star Mergers 2016 Mini-workshop on “Compact Star Mergers and Nucleosynthesis” November 9, 2016

Nuclear Astrophysics Virtual Institute

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Outline

1

Introduction

2

Nucleosynthesis in supernova neutrino-driven winds

3

Nucleosynthesis in neutron star mergers Dynamical ejecta Accretion disk ejecta

4

Summary

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

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.

20 40 60 80 100 120 140 160 180 200 220

Mass Number

10−2 100 102 104 106 108 1010

Abundance relative to Silicon = 106

He D H Li Be B CO NeSi S Ca Fe Ni Ge Sr Xe Ba Pt Pb r s r s

Sneden, Cowan & Gallino 2008

Core-collapse Supernovae

[Mg/Fe] [Eu/Fe] [Fe/H] 1.5 1.0 0.5 – 0.5 1.5 1.0 0.5 – 0.5 –3 –2 –1

a b

T y p e I a

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Heavy elements and metal-poor stars

Cowan & Sneden, Nature 440, 1151 (2006)

30 40 50 60 70 80 90

Atomic Number

−8 −6 −4 −2

Relative log ε

30 40 50 60 70 80 90 −8 −6 −4 −2

Stars rich in heavy r-process elements (Z > 50) and poor in iron (r-II stars, [Eu/Fe] > 1.0). Robust abundance patter for Z > 50, consistent with solar r-process abundance. These abundances seem the result of events that do not produce iron. [Qian & Wasserburg,

• Phys. Rept. 442, 237 (2007)]

Possible Astrophysical Scenario: Neutron star mergers. Stars poor in heavy r-process elements but with large abundances of light r-process elements (Sr, Y, Zr) Production of light and heavy r-process elements is decoupled. Astrophysical scenario: neutrino-driven winds from core-collapse supernova

40 50 60 70 80

Atomic Number (Z)

• 3.5
• 3
• 2.5
• 2
• 1.5
• 1
• 0.5

0.5

log ε (Z)

Eu HD 122563 (Honda et al. 2006) translated pattern of CS 22892-052 (Sneden et al. 2003) Ag Y Pd Mo Ru Nb Sr Zr (b)

Honda et al, ApJ 643, 1180 (2006)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

r-process astrophysical sites

Core-collapse supernova Neutrino-winds from protoneutron stars. Aspherical explosions, Jets, Magnetorotational Supernova, ... [Winteler et al, ApJ 750, L22 (2012); Mösta et al, arXiv:1403.1230 ] Neutron star mergers Mergers are expected to eject around 0.01 M⊙ of neutron rich-material. Similar amount ejected from accretion disk. Observational signature: electromagnetic transient from radioactive decay of r-process nuclei [KiloNova, Metzger et al (2010), Roberts et al (2011), Bauswein et al (2013)]

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Role of weak interactions

Main processes: νe + n ⇄ p + e− ¯ νe + p ⇄ n + e+ Neutrino interactions determine the proton to neutron ratio. Neutron-rich ejecta:

E¯

νe − Eνe > 4∆np −

• L¯

νe

Lνe − 1

E¯

νe − 2∆np

• neutron-rich ejecta: r-process

proton-rich ejecta: νp-process

We need accurate knowledge of νe and ¯ νe spectra Energy difference related to nuclear symmetry energy (GMP et al 2012, Roberts et al 2012)

฀

• α, n

α, p α, p, nuclei α, n, nuclei R in km 102 103 104 105 Rν 3 1.4 He Ni Si PNS O Rns ~10 Neutrino cooling and Neutrino-driven wind n, p νp-process r-process M(r) in M νe,µ,τ, νe,µ,τ νe,µ,τ, νe,µ,τ –

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Constraints in the symmetry energy

Combination nuclear physics experiments and astronomical

• bservations (Lattimer & Lim 2013)

Isobaric Analog States (Danielewicz & Lee 2013) Chiral Effective Field Theory calculations (Drischler+ 2014)

0.01 0.1

nB (fm−3)

5 10 15 20 25 30 35 40

Esym (MeV)

χEFT (NN+3N), Drischler et al 2014 Danielewicz & Lee 2013 IAS Danielewicz & Lee 2013 IAS + Skins Lattimer & Lim 2013 DD2 NL3 TM1 TMA SFHo SFHx FSUgold IUFSU LS180 LS220

Figure data from Matthias Hempel (Basel)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Impact on neutrino luminosities and Ye evolution

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

2 4 6 8 10 Time [s] 1050 1051 1052 Luminosity [ergs/s] 2 4 6 8 10 Time [s] 6 7 8 9 10 11 12 13 Eν [MeV] νe ¯ νe νx 2 4 6 8 10 Time [s] 0.46 0.48 0.50 0.52 0.54 0.56 0.58 0.60 Electron fraction 2 4 6 8 10 Time [s] 20 30 40 50 60 70 80 90 100 Entropy [kB/baryon]

Ye is moderately neutron-rich at early times and later becomes proton-rich.

GMP, Fischer, Huther, J. Phys. G 41, 044008 (2014).

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Nucleosynthesis

50 60 70 80 90 100 110 Mass number A

10−4 10−3 10−2 10−1 100 101 102 103 104 105 106 107

• Rel. abundance

11.2 25 30 35 40 45 50 55 Charge number Z

10−9 10−8 10−7 10−6 10−5 10−4 10−3 10−2

Elemental abundance

HD 122563

Elements between Zn and Mo (A ∼ 90) are produced Mainly neutron-deficient isotopes are produced Uncertainties: Equation of State, neutrino reactions (mainly ¯ νe), Neutrino

• scillations(?).

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Impact opacities on Ye

Weak magnetism and inverse neutron decay (¯ νe + e− + p → n) have a strong impact on Ye 0.5 1 2 3 5 10 0.48 0.5 0.52 0.54 0.56 0.58 t − tbounce [s] Ye

• Ref. run

+ weak magn. + wm + n decay 20 40 60 80 S [kB/baryon] S Y

e

Fischer, GMP,Wu, Lohs, Qian, in preparation

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Neutron star mergers: Short gamma-ray bursts and r-process

x [km] y [km] 12.1235 ms −30 −20 −10 10 20 30 −30 −20 −10 10 20 30 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 x [km] y [km] 12.6867 ms −30 −20 −10 10 20 30 −30 −20 −10 10 20 30 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 x [km] y [km] 13.4824 ms −30 −20 −10 10 20 30 −30 −20 −10 10 20 30 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 x [km] y [km] 15.167 ms −50 50 −50 −40 −30 −20 −10 10 20 30 40 50 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5

Bauswein, Goriely, Janka, ApJ 773, 78 (2013)

Mergers are expected to eject dynamically around 0.001-0.01 M⊙ of neutron rich-material. Impact of weak interactions remains to be understood.

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Dynamical evolution in mergers

Inspiral of NS binary Neutron star merger Prompt formation of a BH + torus Formation of a differentially rotating massive NS Rigidly rotating (supermassive) NS Delayed collapse to a BH + torus

dependent on EoS, Mtot dependent on EoS, Mtot ~100 Myrs ms ms 10-100 ms

Dynamics

Reviews: Duez 2010, Faber & Rasio 2012

secular (disk) ejecta secular (disk) ejecta secular (disk) ejecta dynamical ejecta dynamical ejecta GW → binary masses, EoS GW → EoS

From A. Bauswein.

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Neutron star mergers: Short gamma-ray bursts and r-process

Fernández & Metzger, 2016

A similar amount of material less neutron rich Ye 0.2 is expected to be ejected from the disk. Conditions and ejection mechanism depend on central object (neutron star

• r black hole).

Both dynamical and disk ejecta may contribute to radioactive electromagnetic transient (kilonova).

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Making Gold in Nature: r-process nucleosynthesis

100 150 200 250 10

−3

10

−2

10

−1

10 10

1

r−process waiting point (ETFSI−Q) Known mass Known half−life N=126 N=82

S

• l

a r r a b u n d a n c e s

r−process path

N=184

The r-process requires the knowledge of the properties of extremely neutron-rich nuclei: Nuclear masses. Beta-decay half-lives. Neutron capture rates. Fission rates and yields.

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Evolution nucleosynthesis in mergers

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

• f astrophysical conditions and nuclear

input

Mendoza-Temis, Wu, Langanke, GMP, Bauswein, Janka, PRC 92, 055805 (2015)

528 trajectories

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Final abundances different mass models

10-8 10-7 10-6 10-5 10-4 10-3

abundances at 1 Gyr FRDM

10-8 10-7 10-6 10-5 10-4 10-3 120 140 160 180 200 220 240

abundances at 1 Gyr mass number, A HFB21 WS3

120 140 160 180 200 220 240

mass number, A DZ31

Mendoza-Temis, Wu, Langanke, GMP, Bauswein, Janka, PRC 92, 055805 (2015)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Temporal evolution (selected phases)

Abundance distribution mainly determined by fission from material accumulated in superheavy region.

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Beta decays and r process

Beta-decay half-lives the speed of matter flow from light to heavy nuclei. In the astrophysical environment competition between nuclear time scales (beta decays) and hydrodynamical time scales (expansion). Radioactive beam facilities (present RIKEN, future FRIB and FAIR) are reaching the r-process relevant regions. RIKEN has recently measured 110 half-lives around N = 82 [Lorusso et al, PRL 114, 192501 (2015)]

64 68 72 76 80 84 88

neutron number

0.1 1 10

Tcalc./Texp.

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn

FRDM

Data implies shorter half-lives than commonly used in r-process simulations [FRDM+QRPA: Möller et al., PRC 67, 055802 (2003)]

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

New global calculation of beta-decay half-lives

New global calculation of beta-decay half-lives for r-process nuclei [T. Marketin, L. Huther, GMP, PRC 93, 025805 (2016)] Good agreement with RIKEN data. Substantially shorter half lives for nuclei with (Z 80)

64 68 72 76 80 84 88

neutron number

0.1 1 10

Tcalc./Texp.

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn

D3C*

10 20 30 40 50 60 70 80 90 100 110 120

proton number

20 40 60 80 100 120 140 160 180 200 220 240

neutron number

• 5

+5

log10 T D3C∗

1/2

/T FRDM

1/2

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Impact on r-process abundances (dynamical ejecta)

Shorter half-lives for Z 80 have a strong impact on the position of A ∼ 195 [Eichler et al., ApJ 808, 30 (2015)]

10-7 10-6 10-5 10-4 10-3 10-2 120 140 160 180 200 220 240

abundances at 1 Gyr mass number, A

FRDM masses solar r abundance FRDM+QRPA D3C* 10-7 10-6 10-5 10-4 10-3 10-2 120 140 160 180 200 220 240

abundances at 1 Gyr mass number, A

DZ31 masses solar r abundance FRDM+QRPA D3C*

They also affect the robustness of the distribution and the shape of the 2nd peak (Wu+, in preparation)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Actinides affect opacities and energy production

Actinides can be an important opacity source at timescales of weeks (Mendoza-Temis et al 2015) Important contribution to energy production via alpha decay (Barnes et al 2016)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Nucleosynthesis in black-hole accretion disk ejecta

Accretion disk around compact

• bject is expected to eject material

with broad Ye distribution [Fernández, Metzger, MNRAS 435, 502 (2013)] This material is expected to contribute to the production of all r-process nuclides [Wu et al, MNRAS 463, 2323 (2016)]

0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.15 0.2 0.25 0.3 0.35 0.4

ejecta mass (10-4 M) Ye,5 )

10-7 10-6 10-5 10-4 10-3 10-2 50 100 150 200 250 300

abundances at 1 Gyr mass number, A

solar r abundance FRDM masses DZ31 masses 10-7 10-6 10-5 10-4 10-3 10-2 50 100 150 200 250 300

abundances at 1 Gyr mass number, A

solar r abundance FRDM+QRPA D3C*

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Broad range of disk models considered

Despite variations in black-hole mass, spin, disk mass, viscosity, entropy and Ye models produce all r-process nuclides

10-7 10-6 10-5 10-4 10-3 10-2

abundances at 1 Gyr

(a) solar r abundances S-def m0.01 m0.10 (b) solar r abundances S-def M10 r75 (c) solar r abundances S-def s10 s6 10-7 10-6 10-5 10-4 10-3 50 100 150 200

abundances at 1 Gyr mass number, A

(d) solar r abundances S-def α0.01 α0.10 50 100 150 200

mass number, A

(e) solar r abundances S-def y0.05 y0.15 50 100 150 200

mass number, A

(f) solar r abundances S-def χ0.8

Wu et al, MNRAS 463, 2323 (2016)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Comparison with metal poor stars

Except for elements around Z ∼ 40 (A ∼ 90) disk ejecta produce all r-process nuclides.

• 3
• 2
• 1

1 2 3 30 40 50 60 70 80

logε charge number, Z

CS22892 HD160617 HD122563 S-def s10 s6 10-7 10-6 10-5 10-4 10-3 10-2 50 100 150 200 250

abundances at 1 Gyr mass number, A

S-def s6 s10

Heavy r-process shows robust abundance pattern Wu et al, MNRAS 463, 2323 (2016)

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Effect r-process heating

Some of the models shows anomalous abundance peak at 132Sn due to convection in the disk. Material is partly reheated after neutron exhaustion. Nuclear energy production by the r process suppresses the last reheating phase.

1015 1016 1017 1018 1019 1020 0.1 1 10

nuclear heating rate (erg/g/s) temperature (GK)

ε=1.0 ε=10.0 ε=0.1 10-7 10-6 10-5 10-4 10-3 10-2 50 100 150 200 250

abundances at 1 Gyr mass number, A

S-def ε0.1 ε1.0 ε10.0

5 10 127 130 133 ×10-4

Introduction Nucleosynthesis in supernova neutrino-driven winds Nucleosynthesis in neutron star mergers Summary

Summary

Neutrino-winds from core-collapse are expected to produce elements between Zn and Mo (A ∼ 90). Within present uncertainties on equation of state and neutrino-matter interactions no substantial production of heavier elements is expected. Is the weak r-process excluded from typical supernova? Fission plays a fundamental role in determining the final abundance pattern in dynamical ejecta. Ejecta from black-hole accretion produce all r process elements independently of the contribution from dynamical ejecta. Role of nuclear physics remains to be explored. Kilonova observations will provide a direct proof that the r process

• ccurs in mergers.