1
EXPLOSIVE NUCLEOSYNTHESIS IN
CORE COLLAPSE SUPERNOVAEMarco Limongi
INAF - Osservatorio Astronomico di Roma, ITALY [email protected]
Alessandro ChieffiINAF - Istituto di Astrofisica Spaziale e Fisica
Cosmica, ITALY [email protected]
2PRE-SUPERNOVA STAGE
The Fe core is partially degenerate
The pressure due to degenerate electrons dominate
3THE PATH TO THE EXPLOSIONPhotodisintegrations and Electron Captures Highly degenerate zone exceeds the Chandrasekhar Mass from a fast contraction to a collapse Highly degenerate zone
Fe core
Limiting Mass
4THE PATH TO THE EXPLOSIONPhotodisintegrations and Electron Captures Highly degenerate zone exceeds the Chandrasekhar Mass from a fast contraction to a collapseCollpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and rebounds
Woosley & Janka 2008
5THE PATH TO THE EXPLOSIONPhotodisintegrations and Electron Captures Highly degenerate zone exceeds the Chandrasekhar Mass from a fast contraction to a collapseCollpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and reboundsPrompt shock wave forms and propagates through the outer core – During this propagation it dissociates Fe nuclei into free nucleons and loses
Woosley & Janka 2008
6THE PATH TO THE EXPLOSIONPhotodisintegrations and Electron Captures Highly degenerate zone exceeds the Chandrasekhar Mass from a fast contraction to a collapseCollpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and reboundsPrompt shock wave forms and propagates through the outer core – During this propagation it dissociates Fe nuclei into free nucleons and loses The shock consumes its entire kinetic energy still within the Fe core - It turns into an accretion shock at a radius between 100 and 200 km and the Explosion Fails
7THE PATH TO THE EXPLOSIONPhotodisintegrations and Electron Captures Highly degenerate zone exceeds the Chandrasekhar Mass from a fast contraction to a collapseCollpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and reboundsPrompt shock wave forms and propagates through the outer core – During this propagation it dissociates Fe nuclei into free nucleons and loses The shock consumes its entire kinetic energy still within the Fe core - It turns into an accretion shock at a radius between 100 and 200 km and the Explosion FailsLots of neutrinos are emitted from the newly forming neutron star at the center - The persistent neutrino energy deposition behind the shock keeps the pressure high in this region and drives the shock outwards again, eventually leading to a supernova explosion.
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The most recent and detailed simulations of core collapse SN explosions show that:
the shock still stalls No explosion is obtainedthe energy of the explosion is a factor of 3 to 10 lower than usually observedWork is underway by all the theoretical groups to better
understand the problem and we may expect progresses in the next future
The simulation of the explosion of the envelope is needed to have information on:
the chemical yields (propagation of the shock wave compression and heating explosive nucleosynthesis)the initial mass-remnant mass relation
THE CURRENT CCSN MODELSAfter two decades of research the paradigm of the neutrino driven wind explosion mechanism is widely accepted, but….
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Propagation of the shock wave through the
envelope
Compression and
HeatingExplosive
Nucleosynthesis
The explosive nucleosynthesis calculations for core collapse supernovae are still based on explosions induced by injecting an arbitrary amount of energy in a (also arbitrary) mass location of the presupernova model and then following the development of the blast wave by means of an hydro code.
• Piston
• Thermal Bomb
• Kinetic Bomb
EXPLOSIVE NUCLEOSYNTHESIS
10EXPLOSION AND FALLBACK
Matter Falling Back
Mass Cut
Initial Remnan
t
Final Remnant
Matter Ejected into the ISMEkin1051 erg
• Piston (Woosley & Weaver)• Thermal Bomb (Nomoto & Umeda)• Kinetic Bomb (Chieffi & Limongi)
Different ways of inducing the explosion
FB depends on the binding energy: the higher is the initial mass the higher is the binding energy
Fe core
Shock WaveCompression and Heating
Induced Expansion
and Explosion
Initial Remnan
t
Injected Energy
11BASIC PROPERTIES OF THE EXPLOSION• Behind the shock, the pressure is dominated by
radiation• The shock propagates adiabatically
rT1
Fe core
r2
T2
r1
Shock
The peak temperature does not depend on the stellar structure
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Since nuclear reactions are very temperature sensitive, this cause nucleosynthesis to occur within few seconds that might otherwise have taken days or years in the presupernova evolution.
CHARACTERISTIC EXPLOSIVE BURNING TEMPERATURES
Where in general:
The typical burning timescale for destruction of any given fuel is:
13CHARACTERISTIC EXPLOSIVE BURNING TEMPERATURES
These timescales for the fuels He, C, Ne, O, Si are determined by the major destruction reaction:
and in general are function of temperature and density:
He burning:
C burning:
Ne burning:
O burning:
Si burning:
14CHARACTERISTIC EXPLOSIVE BURNING TEMPERATURES
If we take typical explosive burning timescales of the order of 1s
Explosive C burningExplosive Ne burningExplosive O burningExplosive Si burning
Thielemann et al. 1998
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5000
Explosive O burning
6400
Explosive Ne burning
11750
Explosive C burning
13400RADIUS (Km)
No M
odifi
catio
n
By combining the properties of the matter at high temperature and the basic properties of the explosion we
expect
Explosive Si burning
This is independent of the details of the progenitor star
16ROLE OF THE PROGENITOR STAR• Mass-Radius relation @ Presupernova
Stage:determines the amount of mass contained in each volume determines the amount of mass processed by each explosive burning.
Explosive O burning
Explosive Ne burning
Explosive C burning
No M
odifi
catio
nExplosive Si burning
INTERIOR MASS
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• The Ye profile at Presupernova Stage:it is one of the quantities that determines the chemical composition of the more internal zones that reach the NSE/QSE stage
ROLE OF THE PROGENITOR STAR• Mass-Radius relation @ Presupernova
Stage:determines the amount of mass contained in each volume determines the amount of mass processed by each explosive burning.
Ye=0.50 56Ni=0.63 – 55Co=0.11 – 52Fe=0.07 – 57Ni=0.06 – 54Fe=0.05Ye=0.49 54Fe=0.28 – 56Ni=0.24 – 55Co=0.16 – 58Ni=0.11 – 57Ni=0.08
T=5∙109 K r=108 g/cm3
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• The Ye profile at Presupernova Stage:it is one of the quantities that determines the chemical composition of the more internal zones that reach the NSE/QSE stage
• The Chemical Composition at Presupernova Stage:it determines the final composition of all the more external regions undergoing explosive (in non NSE/QSE regine)/hydrostatic burnings
ROLE OF THE PROGENITOR STAR• Mass-Radius relation @ Presupernova
Stage:determines the amount of mass contained in each volume determines the amount of mass processed by each explosive burning.
19THE HYDRODYNAMICSSets the details of the physical conditions (temporal evolution of Temperature and Density) for each explosive burning the detailed products of each explosive burning
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• For T>5 109 K all the forward and the reverse strong reactions (with few exceptions) come to an equilibrium and a NSE distribution is quickly established
COMPLETE EXPLOSIVE SI BURNING
In this condition the abundance of each nucleus is given by:
These equations have the properties of favouring the more bound nucleus corresponding to the actual neutrons excess.
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jlik rr
i + k j + l
),max()(
jlik
jlik
rr
rrij
0)( ij
No equilibrium1)( ij
Full equilibrium
Since the matter exposed to the explosion has Ye>0.49
(h<0.02)
Most abundant isotope 56Ni
Elements also produced: Ti (48Cr) , Co (59Ni), Ni (58Ni)
COMPLETE EXPLOSIVE SI BURNING
22INCOMPLETE EXPLOSIVE SI BURNING• Temperatures between 4 109 K < T < 5 109 K are not high enough to
allow a complete exhaustion of 28Si, although the matter quickly reaches a NSE distribution
Main products: Ti (48Cr), V (51Cr), Cr (52Fe), Mn (55Co)
23EXPLOSIVE O BURNING• Temperatures between 3.3 109 K < T < 4 109 K are not high
enough to allow a full NSE
• Two equilibrium clusters form separted at the level of the bottleneck @ A=44
• Since the matter exposed to the explosion has A<44 and since there is a very small leackage through the bottleneck @ A=44, the path to the heavier elements is severely inhibited
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• Temperatures between 3.3 109 K < T < 4 109 K are not high enough to allow a full NSE
• Two equilibrium clusters forms separted at the level of the bottleneck @ A=44
• Since the matter exposed to the explosion has A<44 and since there is a very small leackage through the bottleneck @ A=44, the path to the heavier elements is severely inhibited
Main products: Si (28Si), S (32S) , Ar (36Ar), Ca (40Ca)
EXPLOSIVE O BURNING
25EXPLOSIVE C/NE BURNING• If T < 3.3 109 K the processes are far from the
equilibrium and nuclear processing occur through a well defined sequence of nuclear reactions.
Elements preferrentially synthesized in these conditions over the typical eplosion timescales:
• If T < 1.9 109 K no nuclear processing occur over the typical explosion timescales.
Si (28Si), P (31P), Cl (35Cl), K (39K), Sc (45Sc)
26COMPOSITION OF THE EJECTAEXPLOSIVE BURNINGS
Limongi & Chieffi 2006
27Hydrostatic Production Explosive Production Core He burning C
ShellC/Ne O Si-i Si-c
Si (28Si) 50 50P (31P) 15 25 60
S (32S) 30 30 35
Cl (60% 35Cl - 40% 37Cl) 35Cl 37Cl 100
100
Ar (36Ar) 30 70
K (39K) 70 20
Ca (40Ca) 15 75
Sc (45Sc) 35 25 35
Ti (30% 46Ti - 60% 48Ti) 46Ti 48Ti (48Cr)
50 4060 40
V [51V (51Cr)] 20 60 10
Cr [52Cr (20% 52Mn - 80% 52Fe) 52Mn 52Fe
6565
3535
Mn [55Mn (20% 55Fe - 80% 55Co) 55Fe 55Co
60 2070
2030
Fe [56Fe (56Ni)] 10 90
Co [59Co (80% 59Co - 20% 59Ni) 59Co 59Ni
50 50100
Ni (80% 58Ni - 20% 60Ni) 58Ni 60Ni
100100
This
pict
ure
may
cha
nge
sligh
tly b
y ch
angi
ng th
e in
itial
mas
s and
/or
met
allic
ity
Limongi & Chieffi 2006
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During the propagation of the shock wave through the mantle some amount of matter may fall back onto the compact remnant
It depends on the binding energy of the star and on the final kinetic
energy
FALLBACK AND FINAL REMNANT
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Sic
Sc,Ti,FeCo,Ni
56Ni
Sii
Cr,V,Mn
56Ni
Ox
Si,S,ArK,Ca
Fe Core
Initial Mass Cut
Sic
Sc,Ti,FeCo,Ni
56Ni
Sii
Cr,V,Mn
56Ni
Si,S,ArK,Ca
Fe Core
Ox
Initial Mass Cut
Sic
Sc,Ti,FeCo,Ni
56Ni
Sii
Si,S,ArK,Ca
56Ni
Cr,V,Mn
Ox
Sic
Sc,Ti,FeCo,Ni
56Ni
Sii
Cr,V,Mn
56Ni
Si,S,ArK,Ca
Ox
Final Mass Cut
THE EJECTION OF 56NI AND HEAVY ELEMENTS
The amount of 56Ni and heavy elements strongly depends on the Mass Cut
Remnant
30THE EJECTED 56NIIn absence of mixing a high kinetic energy is required to
eject even a small amount of 56Ni
31MIXING BEFORE FALLBACK MODEL
56Ni and heavy elements can be ejected even with extended fallback
Sic
Sc,Ti,FeCo,Ni
56Ni
Sii
Cr,V,Mn
56Ni
Ox
Si,S,ArK,Ca
Fe Core
Initial Mass Cut
Sic
Sc,Ti,FeCo,Ni
Sii
Cr,V,Mn
56Ni
Ox
Si,S,ArK,Ca
Mixing RegionFe Core
Initial Mass Cut
Sic
Sc,Ti,FeCo,Ni
Sii
Cr,V,Mn
56Ni
Ox
Si,S,ArK,Ca
Mixing Region
Final Mass Cut
Isotopes produced in
the innermost
zones
Remnant
56Ni 56Ni
56Ni
56Ni
56Ni
56Ni
56Ni
56NiUmeda & Nomoto 2003
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No Mas
s Loss
Final Ma
ss
He-Cor
e Mass
He-CC
Mass
CO-Core Mass
Fe-Core Mass
WNL
WNE WC/WO
Remnan
t Mass
Neutron Star
Black Hole
SNII SNIb/c
Fallba
ck
RSG
Z=Z
E=1051 ergNL00 WIND
THE FINAL FATE OF A MASSIVE STAR
Limongi & Chieffi 2007
33THE YIELDS OF MASSIVE STARS
Limongi & Chieffi 2006
34THE YIELDS OF MASSIVE STARS
Limongi & Chieffi 2006
35CHEMICAL ENRICHMENT DUE TO A SINGLE MASSIVE STAR
The Production Factors (PFs) provide information on the global enrichment of the matter and its distribution
Solar MetallicityModels
36CHEMICAL ENRICHMENT DUE TO A GENERATION OF MASSIVE STARS
Yields averaged over a Salpeter IMF
The integration of the yields provided by each star over an initial mass function provide the chemical composition of the
ejecta due to a generation of massive stars
Production Factors averaged over a
Salpeter IMF
37CHEMICAL ENRICHMENT DUE TO A GENERATION OF MASSIVE STARS
Massive stars contribute significantly to the production of elements from C to Sr (~2 < PF( C < Z < Sr ) < ~11)Elements produced by explosive burnings are almost co-produced with O and also in roughly solar proportions except for the Fe peak elementsMassive stars contribute to the production of the Fe peak elements for about 30% of the global production.
Limongi & Chieffi 2007
38SUMMARY
Assuming a Salpeter IMF, massive stars contribute significantly to the production of elements from C to Sr (~2 < PF( C < Z < Sr ) < ~11)
Explosive nucleosynthesis (EN) occurs in the innermost zones (R<13500 km) of the exploding envelope (above the Fe core) of any massive starEN modifies significantly the presupernova abundances and is responsible for the production of all the elements from Si to Ni (with few exceptions)Because of the large binding energy, and hence large remnant masses, stars with M>30 M do not contribute to the enrichment of elements produced by EN
Elements produced by explosive burnings are almost co-produced with O and also in roughly solar proportions except for the Fe peak elementsMassive stars contribute to the production of the Fe peak elements for about 30% of the global production.
39MAIN UNCERTAINTIES IN THE EXPLOSIVE NUCLEOSYNTHESIS
All the uncertainties connected with the induced explosion model (how to kick the blast wave, where to inject the initial energy and in which form) How much energy required to infinity amount of fall back, freezoutTreatment of fallback (multidimensional calculations, jet induced explosions)Weak interactions working during the presupernova stages Ye profile chemical composition where NSE/QSE is reached during the explosion
Lack of selfconsistent model for core collapse explosion
4044TI NUCLEOSYNTHESIS
CasA as seen by IBIS/ISGRI onboard INTEGRALDistance 3 Kpc -- 335 yr old -- Mini 30 M Mend
16 M 3 lines : 67.9 KeV, 78.4 KeV, 1.157 MeVObserved: M(44Ti)=1.6 10-4 M
Predicted: M(44Ti)=3.0 10-5 M
Reanud et al. 2006
4144TI NUCLEOSYNTHESISNo production in normal freezout
4244TI NUCLEOSYNTHESISProduction in a-rich freezout
43THE ROLE OF THE MORE MASSIVE STARS
Large Fall Back
Mass Loss Prevents Destruction
Which is the contribution of stars with M ≥ 35 M?
They produce:~60% of the total C and N (mass loss)~40% of the total Sc and s-process elements (mass loss)No intermediate and iron peak elements (fallback)
44CHEMICAL ENRICHMENT DUE TO MASSIVE STARS
The average metallicity Z grows slowly and continuously with respect to the evolutionary timescales of the stars that contribute to the
environment enrichment
Most of the solar system distribution is the result (as a first approximation) of the ejecta of ‘‘quasi ’’–solar-
metallicity stars.
The PFs of the chemical composition provided by a generation of solar metallicity stars should be
almost flat
45CHEMICAL ENRICHMENT DUE TO MASSIVE STARS
Secondary Isotopes?
No room for other sources (AGB)
Remnant Masses? Type IaAGB?
n process. Other sources
uncertainExplosion?
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THE END