NUCLEOSYNTHESIS IN STELLAR EVOLUTION AND EXPLOSIONS: ABUNDANCE YIELDS FOR CHEMICAL EVOLUTION' MASSIV

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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 Email
marco_at_oa-roma.inaf.it
Work with
Alessandro Chieffi
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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 zgt5
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
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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

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H burning
Mmin(O) 14 M?
t(O)/t(H burning) 0.15 (14 M? ) 0.79 (120 M?)
MASS LOSS
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Hs0.695
Cs3.18 10-3
Hes0.285
Ns1.16 10-3
Os1.00 10-2
t6.8 106 yr
t2 107 yr
1H ? 4He
1H ? 4He
CNO ? 13C,14N, 17O NeNa,MgAl ? 23Na, 26Al
CNO ? 13C,14N, 17O NeNa,MgAl ? 23Na, 26Al
WIND
t3.6 106 yr
WIND
WNL
t2.7 106 yr
1H ? 4He
1H ? 4He
CNO ? 13C,14N, 17O NeNa,MgAl ? 23Na, 26Al
CNO ? 13C,14N, 17O NeNa,MgAl ? 23Na, 26Al
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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
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He burning
The properties of core He burning mainly depend
on the size of the He core
M 35 M? ? RSG
M gt 35 M? ? BSG
g
g
g
3a 12C(a,g)16O
g
g
g
g
g
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11
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t2.0 107 yr
t1.5 106 yr
t6.8 106 yr
t5.3 105 yr
4He, 14N
4He, 14N
4He ? 12C, 16O 22Ne, s-proc
4He ? 12C, 16O 22Ne, s-proc
120
60
WNL
t3.6 106 yr
t3.6 105 yr
t2.7 106 yr
t3.0 105 yr
WNL
WNE
WNE
WC
WC
4He, 12C
4He, 12C
4He ? 12C, 16O 22Ne, s-proc
4He ? 12C, 16O 22Ne, s-proc
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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
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Advanced burning stages
Neutrino losses play a dominant role in the
evolution of a massive star beyond core He burning
At high temperature (Tgt109 K) neutrino emission
from pair production start to become very
efficient
Evolutionary times reduce dramatically
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M lt 30 M? ? Explode as RSG
M 30 M? ? Explode as BSG
After core He burning
At Pre-SN stage
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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
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Synthesis of Heavy Elements
Weak Interactions become efficient
O-burning
Efficiency scales inversely with the mass
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Synthesis of Heavy Elements
At Oxygen exhaustion
Balance between forward and reverse reactions for
increasing number of processes
a b
c d
At Oxygen exhaustion
At Si ignition
Sc
Si
Equilibrium
Equilibrium
Partial Eq.
Out of Eq.
Out of Equilibrium
56,57,58Fe, 52,53,54Cr, 55Mn, 59Co, 62Ni NSE
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H
11 M?
25 M?
H
He
He
103 yr
3yr
0.3yr
5 days
CO
CO
O
Ne/O
Si
Ne/O
O
Fe
Si
Fe
H
H
60 M?
120 M?
He
He
CO
CO
Ne/O
Ne/O
O
O
Si
Si
Fe
Fe
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Chemical Composition at the PreSN stage
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Final Masses at the PreSN stage
HEAVY ELEMENTS
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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

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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
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
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The Final Fate of a Massive Star
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RADIATION DOMINATED
NSE/QSE
Si-c
Si-i
Ox
Ne/Cx
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Individual Yields
Different chemical composition of the ejecta for
different masses
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Averaged Yields
Yields averaged over a Salpeter IMF
Global Properties
Initial Composition (Mass Fraction)
Final Composition (Mass Fraction)
NO Dilution
Mrem0.186
X0.695 Y0.285 Z0.020
X0.444 (f0.64) Y0.420 (f1.47) Z0.136
(f6.84)
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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

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Present Status of the presupernova and explosion
modelling of Massive Stars
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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)
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ZZ?
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Global Properties
ZZ?
Final Composition (for each solar mass returned
to the ISM)
LC06
WW95
RHHW02
X0.444 (f0.64) Y0.420 (f1.47) Z0.136
(f6.84)
X0.463 (f0.65) Y0.391 (f1.42) Z0.146
(f7.30)
X0.482 (f0.65) Y0.340 (f1.42) Z0.178
(f8.90)
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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 http//www.mporzio.astro.it/limongi