1 E XPLOSIVE N UCLEOSYNTHESIS IN C ORE C OLLAPSE S UPERNOVAE Marco Limongi INAF - Osservatorio Astronomico di Roma, ITALY Alessandro Chieffi INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, ITALY

2 P RE -S UPER N OVA S TAGE The Fe core is partially degenerate The pressure due to degenerate electrons dominate

3 T HE P ATH TO THE E XPLOSION Photodisintegrations and Electron Captures  Highly degenerate zone exceeds the Chandrasekhar Mass  from a fast contraction to a collapse Highly degenerate zone Fe core Limiting Mass

4 T HE P ATH TO THE E XPLOSION Photodisintegrations and Electron Captures  Highly degenerate zone exceeds the Chandrasekhar Mass  from a fast contraction to a collapse Collpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and rebounds Woosley & Janka 2008

5 T HE P ATH TO THE E XPLOSION Photodisintegrations and Electron Captures  Highly degenerate zone exceeds the Chandrasekhar Mass  from a fast contraction to a collapse Collpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and rebounds Prompt shock wave forms and propagates through the outer core – During this propagation it dissociates Fe nuclei into free nucleons and loses Woosley & Janka 2008

6 T HE P ATH TO THE E XPLOSION Photodisintegrations and Electron Captures  Highly degenerate zone exceeds the Chandrasekhar Mass  from a fast contraction to a collapse Collpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and rebounds Prompt 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

7 T HE P ATH TO THE E XPLOSION Photodisintegrations and Electron Captures  Highly degenerate zone exceeds the Chandrasekhar Mass  from a fast contraction to a collapse Collpase proceeds to nuclear densities ( ) – EOS stiffens ( ) – The inner core becomes incompressible, decelerates and rebounds Prompt 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 Lots 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.

8 The most recent and detailed simulations of core collapse SN explosions show that: the shock still stalls  No explosion is obtained the energy of the explosion is a factor of 3 to 10 lower than usually observed Work 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 T HE C URRENT CCSN M ODELS After two decades of research the paradigm of the neutrino driven wind explosion mechanism is widely accepted, but….

9 Propagation of the shock wave through the envelope Compression and Heating Explosive 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 E XPLOSIVE N UCLEOSYNTHESIS

10 E XPLOSION AND F ALLBACK Matter Falling Back Mass Cut Initial Remnant Final Remnant Matter Ejected into the ISM E kin  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 Wave Compression and Heating Induced Expansion and Explosion Initial Remnant Injected Energy

11 B ASIC P ROPERTIES OF THE E XPLOSION Behind the shock, the pressure is dominated by radiation The shock propagates adiabatically r T1T1 Fe core r2r2 T2T2 r1r1 Shock The peak temperature does not depend on the stellar structure

12 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. C HARACTERISTIC E XPLOSIVE B URNING T EMPERATURES Where in general: The typical burning timescale for destruction of any given fuel is:

13 C HARACTERISTIC E XPLOSIVE B URNING T EMPERATURES 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:

14 C HARACTERISTIC E XPLOSIVE B URNING T EMPERATURES If we take typical explosive burning timescales of the order of 1s Explosive C burning Explosive Ne burning Explosive O burning Explosive Si burning Thielemann et al. 1998

Explosive O burning 6400 Explosive Ne burning Explosive C burning RADIUS (Km) No Modification 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

16 R OLE OF THE P ROGENITOR S TAR Mass-Radius 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 Modification Explosive Si burning INTERIOR MASS

17 The Y e 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 R OLE OF THE P ROGENITOR S TAR Mass-Radius Presupernova Stage: determines the amount of mass contained in each volume  determines the amount of mass processed by each explosive burning. Y e =0.50  56 Ni=0.63 – 55 Co=0.11 – 52 Fe=0.07 – 57 Ni=0.06 – 54 Fe=0.05 Y e =0.49  54 Fe=0.28 – 56 Ni=0.24 – 55 Co=0.16 – 58 Ni=0.11 – 57 Ni=0.08 T=5∙10 9 K  =10 8 g/cm 3

18 The Y e 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 R OLE OF THE P ROGENITOR S TAR Mass-Radius Presupernova Stage: determines the amount of mass contained in each volume  determines the amount of mass processed by each explosive burning.

19 T HE H YDRODYNAMICS Sets the details of the physical conditions (temporal evolution of Temperature and Density) for each explosive burning  the detailed products of each explosive burning

20 For T> K all the forward and the reverse strong reactions (with few exceptions) come to an equilibrium and a NSE distribution is quickly established C OMPLETE E XPLOSIVE S I B URNING 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.

21 i + k j + l No equilibrium Full equilibrium Since the matter exposed to the explosion has Y e >0.49 (  <0.02) Most abundant isotope 56 Ni Elements also produced: Ti ( 48 Cr), Co ( 59 Ni), Ni ( 58 Ni) C OMPLETE E XPLOSIVE S I B URNING

22 I NCOMPLETE E XPLOSIVE S I B URNING Temperatures between K < T < K are not high enough to allow a complete exhaustion of 28 Si, although the matter quickly reaches a NSE distribution Main products: Ti ( 48 Cr), V ( 51 Cr), Cr ( 52 Fe), Mn ( 55 Co)

23 E XPLOSIVE O B URNING Temperatures between K < T < K are not high enough to allow a full NSE Two equilibrium clusters form separted at the level of the A=44 Since the matter exposed to the explosion has A<44 and since there is a very small leackage through the A=44, the path to the heavier elements is severely inhibited

24 Temperatures between K < T < K are not high enough to allow a full NSE Two equilibrium clusters forms separted at the level of the A=44 Since the matter exposed to the explosion has A<44 and since there is a very small leackage through the A=44, the path to the heavier elements is severely inhibited Main products: Si ( 28 Si), S ( 32 S), Ar ( 36 Ar), Ca ( 40 Ca) E XPLOSIVE O B URNING

25 E XPLOSIVE C/N E BURNING If T < 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 < K no nuclear processing occur over the typical explosion timescales. Si ( 28 Si), P ( 31 P), Cl ( 35 Cl), K ( 39 K), Sc ( 45 Sc)

26 C OMPOSITION OF THE E JECTA EXPLOSIVE BURNINGS Limongi & Chieffi 2006

27 Hydrostatic ProductionExplosive Production Core He burningC ShellC/NeOSi-iSi-c Si ( 28 Si)50 P ( 31 P) S ( 32 S)30 35 Cl (60% 35 Cl - 40% 37 Cl) 35 Cl 37 Cl100 Ar ( 36 Ar)3070 K ( 39 K)7020 Ca ( 40 Ca)1575 Sc ( 45 Sc) Ti (30% 46 Ti - 60% 48 Ti) 46 Ti 48 Ti ( 48 Cr) V [ 51 V ( 51 Cr)] Cr [ 52 Cr (20% 52 Mn - 80% 52 Fe) 52 Mn 52 Fe Mn [ 55 Mn (20% 55 Fe - 80% 55 Co) 55 Fe 55 Co Fe [ 56 Fe ( 56 Ni)]1090 Co [ 59 Co (80% 59 Co - 20% 59 Ni) 59 Co 59 Ni Ni (80% 58 Ni - 20% 60 Ni) 58 Ni 60 Ni 100 This picture may change slightly by changing the initial mass and/or metallicity Limongi & Chieffi 2006

28 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 F ALLBACK A ND F INAL R EMNANT

29 Si c Sc,Ti,Fe Co,Ni 56 Ni Si i Cr,V,Mn 56 Ni OxOx Si,S,Ar K,Ca Fe Core Initial Mass Cut Si c Sc,Ti,Fe Co,Ni 56 Ni Si i Cr,V,Mn 56 Ni Si,S,Ar K,Ca Fe Core OxOx Initial Mass Cut Si c Sc,Ti,Fe Co,Ni 56 Ni Si i Si,S,Ar K,Ca 56 Ni Cr,V,Mn OxOx Si c Sc,Ti,Fe Co,Ni 56 Ni Si i Cr,V,Mn 56 Ni Si,S,Ar K,Ca OxOx Final Mass Cut T HE E JECTION OF 56 N I AND H EAVY E LEMENTS The amount of 56 Ni and heavy elements strongly depends on the Mass Cut Remnant

30 T HE E JECTED 56 N I In absence of mixing a high kinetic energy is required to eject even a small amount of 56 Ni

31 M IXING B EFORE F ALLBACK M ODEL 56 Ni and heavy elements can be ejected even with extended fallback Si c Sc,Ti,Fe Co,Ni 56 Ni Si i Cr,V,Mn 56 Ni OxOx Si,S,Ar K,Ca Fe Core Initial Mass Cut Si c Sc,Ti,Fe Co,Ni Si i Cr,V,Mn 56 Ni OxOx Si,S,Ar K,Ca Mixing Region Fe Core Initial Mass Cut Si c Sc,Ti,Fe Co,Ni Si i Cr,V,Mn 56 Ni OxOx Si,S,Ar K,Ca Mixing Region Final Mass Cut Isotopes produced in the innermost zones Remnant 56 Ni Umeda & Nomoto 2003

32 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 SNIISNIb/c Fallback RSG Z=Z  E=10 51 erg NL00 WIND T HE F INAL F ATE O F A M ASSIVE S TAR Limongi & Chieffi 2007

33 T HE Y IELDS OF M ASSIVE S TARS Limongi & Chieffi 2006

34 T HE Y IELDS OF M ASSIVE S TARS Limongi & Chieffi 2006

35 C HEMICAL E NRICHMENT DUE TO A S INGLE M ASSIVE S TAR The Production Factors (PFs) provide information on the global enrichment of the matter and its distribution Solar Metallicity Models

36 C HEMICAL E NRICHMENT DUE TO A G ENERATION OF M ASSIVE S TARS 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

37 C HEMICAL E NRICHMENT DUE TO A G ENERATION OF M ASSIVE S TARS 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 elements Massive stars contribute to the production of the Fe peak elements for about 30% of the global production. Limongi & Chieffi 2007

38 S UMMARY 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 star EN 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 elements Massive stars contribute to the production of the Fe peak elements for about 30% of the global production.

39 M AIN U NCERTAINTIES IN THE E XPLOSIVE N UCLEOSYNTHESIS 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, freezout Treatment 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

40 44 T I N UCLEOSYNTHESIS CasA as seen by IBIS/ISGRI onboard INTEGRAL Distance 3 Kpc yr old -- M ini 30 M  M end 16 M  3 lines : 67.9 KeV, 78.4 KeV, MeV Observed: M( 44 Ti)= M  Predicted: M( 44 Ti)= M  Reanud et al. 2006

41 44 T I N UCLEOSYNTHESIS No production in normal freezout

42 44 T I N UCLEOSYNTHESIS Production in  -rich freezout

43 T HE R OLE OF THE M ORE M ASSIVE S TARS 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)

44 C HEMICAL E NRICHMENT DUE TO M ASSIVE S TARS 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

45 C HEMICAL E NRICHMENT DUE TO M ASSIVE S TARS Secondary Isotopes? No room for other sources (AGB) Remnant Masses? Type Ia AGB? process. Other sources uncertain Explosion?

46 THE END