1. NUCLEOSYNTHESIS IN STELLAR EVOLUTION AND EXPLOSIONS: ABUNDANCE YIELDS FOR CHEMICAL EVOLUTION. MASSIVE STARS
Marco Limongi
INAF – Osservatorio Astronomico di Roma, ITALY
and
Centre for Stellar and Planetary Astrophysics
Monash University – AUSTRALIA
Work with:
Alessandro Chieffi

2. Massive Stars, those massive enough to explode as supernovae, play a key role in many fields of astrophysics:
Evolution of Galaxies:
Light up regions of stellar birth  induce star formation
Production of most of the elements (those necessary to life)
Mixing (winds and radiation) of the ISM
Production of neutron stars and black holes
Cosmology (PopIII):
Reionization of the Universe at z>5
Massive Remnants (Black Holes)  AGN progenitors
Pregalactic Chemical Enrichment
High Energy Astrophysics:
Production of long-lived radioactive isotopes:
(26Al, 56Co, 57Co, 44Ti, 60Fe)
GRB progenitors
The understanding of these stars, is crucial for the interpretation of many astrophysical objects

3. Outline
Basic PreSN Evolutionary Properties of Massive Stars and Their Uncertainties
Explosive Nucleosynthesis and its uncertainties
Present Status of the presupernova and explosion modelling of Massive Stars
Comparison among available yields
Strategies for improvements

4. H burning g
H Conv. core
CNO Cycle
Mmin(O) = 14 M
t(O)/t(H burning): (14 M ) – 0.79 (120 M)
MASS LOSS

5. WNL t=6.8 106 yr t=2 107 yr t=3.6 106 yr t=2.7 106 yr Hs=0.695
Cs=
Hes=0.285
Ns=
Os=
t= yr
t=2 107 yr
1H  4He
1H  4He
CNO  13C,14N, 17O
NeNa,MgAl  23Na, 26Al
CNO  13C,14N, 17O
NeNa,MgAl  23Na, 26Al
Hs=0.566
Hes=0.414
Cs=
Ns=
Os=
26Als=2 10-6
Hs=0.194
Hes=0.786
Cs=
Ns=
Os=
26Als=7 10-6
WIND
t= yr
WIND
WNL
t= yr
1H  4He
1H  4He
CNO  13C,14N, 17O
NeNa,MgAl  23Na, 26Al
CNO  13C,14N, 17O
NeNa,MgAl  23Na, 26Al

6. Major Uncertainties in the computation of core H burning models:
Extension of the Convective Core (Overshooting, Semiconvection)
Mass Loss
Both influence the size of the He core that drives the following evolution

7. He burning
The properties of core He burning mainly depend on the size of the He core
M ≤ 35 M  RSG g
M > 35 M  BSG g g 3a +
12C(a,g)16O g g g g g

8. 11 25
Hs=0.649
Hes=0.331
Cs=
Ns=
Os=
t= yr
t= yr
t= yr
t= yr
4He, 14N
4He, 14N
4He  12C, 16O
22Ne, s-proc
4He  12C, 16O
22Ne, s-proc
120
Hs=0.000
Hes=0.516
Cs=0.397
Ns=0.000
Os=0.06
Hs=0.000
Hes=0.422
Cs=0.432
Ns=0.000
Os=0.119 60
WNL
t= yr
t= yr
t= yr
t= yr
WNL
WNE
WNE WC WC
4He, 12C
4He, 12C
4He  12C, 16O
22Ne, s-proc
4He  12C, 16O
22Ne, s-proc

9. Major Uncertainties in the computation of core He burning models:
Extension of the Convective Core (Overshooting, Semiconvection)
Central 12C mass fraction (Treatment of Convection + 12C(a,g)16O cross section)
Mass Loss (determine which stars explode as RSG and which as BSG)
22Ne(a,n)25Mg (main neutron source for s-process nucleosynthesis)
All these uncertainties affect the size of the CO core that drives the following evolution

10. g n Advanced burning stages
Neutrino losses play a dominant role in the evolution of a massive star beyond core He burning
At high temperature (T>109 K) neutrino emission from pair production start to become very efficient n g
Evolutionary times reduce dramatically

11. After core He burning At Pre-SN stage M < 30 M  Explode as RSG
M ≥ 30 M  Explode as BSG
After core He burning
At Pre-SN stage

12. Synthesis of Heavy Elements
At high tempreatures a larger number of nuclear reactions are activated
Heavy nuclei start to be produced
C-burning
Ne-burning

13. Synthesis of Heavy Elements
Weak Interactions become efficient
O-burning
Efficiency scales inversely with the mass

14. Synthesis of Heavy Elements
At Oxygen exhaustion
Balance between forward and reverse reactions for increasing number of processes
a + b
c + d
At Si ignition
(panel a + panel b)
A=44
A=45
Eq. Clusters
28Si
56Fe
At Oxygen exhaustion
At Si ignition Sc Si
Equilibrium
Equilibrium
Partial Eq.
Out of Equilibrium
Out of Eq.
56,57,58Fe, 52,53,54Cr, 55Mn, 59Co, 62Ni
NSE

15. 11 M 25 M 60 M 120 M H H He He 103 yr 3yr 0.3yr 5 days CO CO O
Ne/O Si
“Fe”
Ne/O O Si
“Fe” H H
60 M
120 M He He CO CO
Ne/O
Ne/O O O Si
“Fe” Si
“Fe”

16. Chemical Composition at the PreSN stage
Burning Site
Main Products
Si Burning
56,57,58Fe, 52,53,54Cr, 55Mn, 59Co, 62Ni
O Conv. Shell
28Si, 32S, 36Ar, 40Ca, 34S, 38Ar
C Conv. Shell
20Ne, 23Na, 24Mg,25Mg, 27Al + s-process
He Central
16O, 12C + s-process
He Shell
16O, 12C
H Central+Shell
14N, 13C, 17O
Si burning(Cent.+Sehll)
O conv. Shell
C conv. Shell
He Central
He Shell
H Shell
H Central
16O
28Si
20Ne
12C
4He 1H
“Fe”

17. Final Masses at the PreSN stage
No Mass Loss
Final Mass
He-Core Mass
He-CC Mass
CO-Core Mass
Fe-Core Mass
WNL
WNE
WC/WO
RSG
Radius
WIND
HEAVY ELEMENTS

18. Major Uncertainties in the computation of the advanced burning stages:
Treatment of Convection (interaction between mixing and local burning, stability criterion  behavior of convective shells  final M-R relation  explosive nucleosynthesis)
Computation of Nuclear Energy Generation (minimum size of nuclear network and coupling to physical equations, NSE/QSE approximations)
Weak Interactions (determine Ye  hydrostatic and explosive nucleosynthesis  behavior of core collapse)
Nuclear Cross Sections (nucleosynthesis of all the heavy elements)
Partition Functions (NSE distribution)
Neutrino Losses

19. Explosive Nucleosynthesis and Chemical Yields
Explosion Mechanism Still Uncertain
The explosion can be simulated by means of a piston of initial velocity v0, located near the edge of the iron core
16O
28Si
20Ne
12C
4He 1H
“Fe”
Piston
Si burning
O conv. Shell
C conv. Shell
He Central
He Shell
H Shell
H Central
Piston
Explosion: 1D PPM Lagrangian Hydrocode (Collella & Woodward 1984)
Explosive Nucleosynthesis: same nuclear network adopted in the hydrostatic evolutions
v0 is tuned in order to have a given amount of 56Ni ejected and/or a corresponding final kinetic energy Ekin

20. The Final Fate of a Massive Star
No Mass Loss
Final Mass
He-Core Mass
He-CC Mass
CO-Core Mass
Fe-Core Mass
WNL
WNE
WC/WO
Remnant Mass
Neutron Star
Black Hole
SNII
SNIb/c
Fallback
RSG
Z=Z
E=1051 erg
Initial Mass (M)
Mass (M)

21. RADIATION DOMINATED: f(r,T,Ye) f(r,T,Xi) Sc Ti Fe Co Ni V Cr Mn Si SAr Ca K Ne Na Mg Al P Cl
f(r,T,Ye)
f(r,T,Xi)
NSE/QSE
Si-c
Si-i Ox
Ne/Cx

22. Individual Yields
Different chemical composition of the ejecta for different masses

23. Averaged Yields Yields averaged over a Salpeter IMF Global Properties:
Initial Composition
(Mass Fraction)
NO Dilution
Final Composition
(Mass Fraction)
Mrem=0.186
X=0.695
Y=0.285
Z=0.020
X= (f=0.64)
Y= (f=1.47)
Z= (f=6.84)

24. Major Uncertainties in the simulation of the explosion (remnant mass – nucleosynyhesis):
Prompt vs Delayed Explosion (this may alter both the M-R relation and Ye of the presupernova model)
How to kick the blast wave:
Thermal Bomb – Kinetic Bomb – Piston
Mass Location where the energy is injected
How much energy to inject:
Thermal Bomb (Internal Energy)
Kinetic Bomb (Initial Velocity)
Piston (Initial velocity and trajectory)
How much kinetic energy at infinity (typically ~1051 erg)
Nuclear Cross Sections and Partition Functions

25. Present Status of the presupernova and explosion modelling of Massive Stars
Authors
Mass Range Z
Network
Mass Loss
Rot.
12C(a,g)16O
Convection
Explosion
CL (2004)
13-35
300 itosopes
Fully Coup. (H-Mo) NO
Kunz 2001
Schwarz.
Semi NO
Not Coupled
Hydro/Piston
Prompt
LC (2006)
11-120
0.02
"
YES
Fully Coupled
Hydro(PPM) Kinetic Bomb
WW (1995)
11-40
19 (enuc) +
240 post
(H-Ge)
CF88x1.7
Ledoux
Semiconv.
Delayed
RHHW
(2002)
15-25
(adaptive)
(H-Pb)
Buchmann x 1.2
UN (2002)
13-30
240 coupled ?
CF85
Hydro/Thermal Bomb
NH (1988)+
TNH(1996)
13-25 ?
HMM ( )
9-120
a network for advanced phases
NACRE
Overshooting

26. Databases of Cross Sections
Experimental:
Caughlan et al. (1985)
Caughlan & Fowler (1988)
Angulo et al. (1999) NACRE
Bao et al. (2000): (n,g) reactions
Iliadis et al. (2001): (p,g) reactions
Jaeger et al. (2001): 22Ne(a,n)25Mg
Kunz et al. (2001): 12C(a,g)16O
Formicola et al. (2004) LUNA collaboration: 14N(p,g)15O
LENA collaboration: 14N(p,g)15O
Theoretical:
Woosley et al. 1978
Rauscher & Thielemann (2000) REACLIB
Fuller, Fowler & Newmann (1982,1985) (Weak)
Oda et al. (1984) (Weak)
Takahshi & Yokoi (1987) (Weak)
Langanke & Martinez Pinedo (2000) (Weak)

27. Z=Z
Z=Z

28. Final Composition (for each solar mass returned to the ISM)
Global Properties
Z=Z
Final Composition (for each solar mass returned to the ISM)
LC06
WW95
RHHW02
X= (f=0.64)
Y= (f=1.47)
Z= (f=6.84)
X= (f=0.65)
Y= (f=1.42)
Z= (f=7.30)
X= (f=0.65)
Y= (f=1.42)
Z= (f=8.90)

29. Strategies for improvements
Round Table and Comparison Among:
Evolutionary Codes (Assumptions, Numerical Algorithms, etc.)
Input Physics (EOS, Opacities, Cross Sections, Neutrino Losses, Electron Screenings, etc.)
Nuclear Network (extension, how it is included into the code)
Computation of Models under the same code setup
Input Physics Repository
EOS, Opacities, Cross Sections, etc. (Tables and Codes)
Additional comments welcome......
Pre/Post SN models and explosive yields available at