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MASSIVE STARS: PRESUPERNOVA EVOLUTION, EXPLOSION AND NUCLEOSYNTHESIS

MASSIVE STARS: PRESUPERNOVA EVOLUTION, EXPLOSION AND NUCLEOSYNTHESIS. Marco Limongi INAF – Osservatorio Astronomico di Roma, ITALY and Centre for Stellar and Planetary Astrophysics Monash University – AUSTRALIA Email: marco@oa-roma.inaf.it. What is a Massive star ?.

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MASSIVE STARS: PRESUPERNOVA EVOLUTION, EXPLOSION AND NUCLEOSYNTHESIS

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  1. MASSIVE STARS: PRESUPERNOVA EVOLUTION, EXPLOSION AND NUCLEOSYNTHESIS Marco Limongi INAF – Osservatorio Astronomico di Roma, ITALY and Centre for Stellar and Planetary Astrophysics Monash University – AUSTRALIA Email: marco@oa-roma.inaf.it

  2. What is a Massive star ? It is a star that goes through all the hydrostatic burnings in a quiescent way from H to Si and eventually explodes as a core collapse supernova Mup’ < Massive stars < MPISN >120 8 - 10

  3. Why are Massive stars important in the global evolution of our Universe? 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

  4. BB = Big Bang; CR = Cosmic Rays; neut. = n induced reactions in SNII; IMS = Intermediate Mass Stars; SNII = Core collapse supernovae; SNIa = Termonuclear supernovae; s-r = slow-rapid neutron captures Le SNII contribuiscono in maniera rilevante all’evoluzione chimica della Galassia. Responsabili per la nucleosintesi degli elementi con 16<A<50 and 60<A<90

  5. 60Zn 61Zn 62Zn 63Zn 64Zn 65Zn 66Zn 67Zn 68Zn 57Cu 58Cu 59Cu 60Cu 61Cu 62Cu 63Cu 64Cu 65Cu 66Cu 67Cu 56Ni 57Ni 58Ni 59Ni 60Ni 61Ni 62Ni 63Ni 64Ni 65Ni 54Co 55Co 56Co 57Co 58Co 59Co 60Co 61Co 62Co 52Fe 53Fe 54Fe 55Fe 56Fe 57Fe 58Fe 59Fe 60Fe 61Fe 51Mn 52Mn 53Mn 54Mn 55Mn 56Mn 57Mn 48Cr 49Cr 50Cr 51Cr 52Cr 53Cr 60Co 54Cr 55Cr 45V 46V 47V 48V 49V 50V 51V 52V 60Fe 44Ti 45Ti 46Ti 47Ti 48Ti 49Ti 50Ti 51Ti 41Sc 42Sc 43Sc 44Sc 45Sc 46Sc 47Sc 48Sc 49Sc 50Sc 40Ca 41Ca 42Ca 43Ca 44Ca 45Ca 46Ca 47Ca 48Ca 49Ca 37K 38K 44Ti 39K 40K 41K 42K 35Ar 36Ar 37Ar 38Ar 44Sc 39Ar 40Ar 41Ar 33Cl 34Cl 35Cl 36Cl 37Cl 38Cl 31S 32S 33S 34S 35S 36S 37S 29P 30P 31P 32P 33P 34P (a,g) (a,n) 27Si 28Si 29Si 30Si 31Si 32Si 33Si 3He 4He 25Al 26Al 27Al 28Al 1H 2H 3H 23Mg 24Mg 25Mg 26Mg 27Mg (p,n) (p,g) (a,p) n b-,e+ 21Na 22Na 23Na 24Na 26Al 20Ne 21Ne 22Ne 23Ne (n,g) (g,n) 17F 18F 19F 20F 15O 22Na 16O 17O 18O 19O b+,e- 13N 14N 15N 16N (g,p) (p,a) (n,p) 12C 13C 14C 10B 11B 7Be 8Be 9Be 10Be (g,a) (n,a) 6Li 7Li Computation of the Presupernova Evolution of Massive Stars 1. Extended Network Including a large number of isotopes and reactions (captures of light partcles, e± captures, β± decays)

  6. Computation of the Presupernova Evolution of Massive Stars 2. Strong coupling between physical and chemical evolution: + H/He burnings: Decoupled Coupled Adv. burnings:

  7. Computation of the Presupernova Evolution of Massive Stars 3. Tratment of convection: - Time dependent convection - Interaction between Mixing and Local Burning D = Diffusion Coefficient

  8. Core H burning Convective Core g g g CNO Cycle g g g g g Massive Stars powered by the CNO Cycle The Convective Core shrinks in mass

  9. CNO Cycle 12C + 1H 13N + g 13N  13C + e+ + n 13C + 1H 14N + g 14N + 1H 15O + g 15O  15N + e+ + n 15N + 1H 12C + 4He (99%) 16O + g (1%) CN-Cycle (T  3×107 K) 16O + 1H 17F + g 17F  17O + e+ + n 17O + 1H 14N + 4He NO-Cycle CNO Processed Material C N O

  10. Ne-Na and Mg-Al Cycles During Core H Burning the central temperature is high enough (3-7×107 K) that the Ne-Na and Mg-Al cycles become efficient Ne-Na Cycle Mg-Al Cycle 20Ne + 1H 21Na + g 21Na  21Ne + e+ + n 21Ne + 1H 22Na + g 22Na  22Ne + e+ + n 22Ne + 1H 23Na + g 23Na + 1H 20Ne + 4He 24Mg + 1H 25Al + g 25Al  25Mg + e+ + n 25Mg + 1H 26Al + g 26Al  26Mg + e+ + n 26Mg + 1H 27Al + g 27Al + 1H 24Mg + 4He • 21Na e 25Mg destroyed • 22Ne slightly burnt • 23Na e 26Mg increases • 26Al (~10-7) produced

  11. Evolutionary Properties of the Interior t=6.8 106 yr

  12. Evolutionary Properties of the Surface Core H Burning Models Mmin(O) = 14 M t(O)/t(H burning): 0.15 (14 M ) – 0.79 (120 M)

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

  14. Bordo iniziale CC rad Mix He ad He  C,O Core Convettivo Core He burning 3a+ 12C(a,g)16O 4He + 4He  8Be + g 8Be  4He + 4He 8Be + 4He  12C + g g He Convective Core g g 3 4He  12C + g g g g g g H burning shell H exhausted core (He Core) The He convective core increases in mass

  15. Nucleosynthesis during Core He burning 3 4He  12C + g 12C + 4He  12O + g 16O + 4He  20Ne + g 20Ne + 4He  24Mg + g Chemical composition at core He exhaustion: mainly C/O The C/O ratio is one the quantity that mainl affects the advanced evolution of Massive Stars (it determines the composition of the CO core) C/O ratio depends on: 1. Treatment of convection (late stages of core He burning) 2. 12C(a,g)16O cross section

  16. Nucleosynthesis during Core He burning 14N, produced by H burning activates the sequence of reactions: 14N + 4He  18F + g 18F  18O + e+ + n 18O + 4He  22Ne + g 22Ne + 4He  25Mg + n For the CNO cycle: For e Solar composition XCNO(iniziale)  X14N For a Solat composition at core H exhaustion:X(14N) ~ ½ Z In general: The efficiency of the 14N reactions scales with the metallicity

  17. Nucleosynthesis during Core He burning 14N  22Ne during the initial stages of core He burning He burning H burning CNO (~1/2 Z) 14N (~1/2 Z) 22Ne (~Z) During core He burning, 22Ne is reduced by a factor of ~2 by the nuclear reaction: 22Ne + 4He  25Mg + n Neutron Mass Fraction s-process nucleosynthesis

  18. s-process during Core He burning 78Rb 79Rb 80Rb 81Rb 82Rb 83Rb 84Rb 85Rb p 86Kr 87Kr 88Kr 77Kr 78Kr 79Kr 80Kr 81Kr 82Kr 83Kr 84Kr 85Br 86Br 87Br b- s 76Br 77Br 78Br 79Br 80Br 81Br 82Br 83Br 84Se 85Se 86Se b- 78Se 79Se 80Se 81Se 82Se 75Se 76Se 77Se 83As 84As 85As r b- 74As 75As 76As 77As 78As 79As 80As 81As b 73Ge 74Ge 75Ge 76Ge 77Ge 78Ge 79Ge 80Ge n,g s,r 72Ga 73Ga 74Ga 75Ga 76Ga 77Ga 78Ga 79Ga Both the neutron mass fraction and the seed nuclei abundances scale with the metallicity The abundance of the s-process nuclei scales with the metallicity

  19. Evolutionary Properties of the Interior WIND t=5.3 105 yr

  20. Evolutionary Properties of the Surface Core He Burning Models Core He Burning Models M ≤ 30 M RSG M ≥ 35 M BSG

  21. 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

  22. 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~0.08 MeV) neutrino emission from pair production start to become very efficient g n n He exhausted core (CO Core) g g H burning shell n n H exhausted core (He Core) g g Core Burning g n He burning shell n g g n n g

  23. Advanced burning stages Evolutionary times of the advanced burning stages reduce dramatically

  24. Evolutionary Properties of the Surface M < 30 M Explode as RSG M ≥ 30 M Explode as BSG After core He burning At PreSN stage Absolute Magnitude increases by ~25

  25. Advanced Nuclear Burning Stages: Core C burning H burning shell H He He burning shell CO T~109 K

  26. Advanced Nuclear Burning Stages: C burning At high tempreatures a larger number of nuclear reactions are activated Heavy nuclei start to be produced C-burning Main Products of C burning 20Ne, 23Na, 24Mg, 27Al Scondary Products of C burning s-process nuclesynthesis

  27. Advanced Nuclear Burning Stages: Core Ne burning H burning shell H He burning shell He CO NeO C burning shell T~1.3×109 K

  28. Advanced Nuclear Burning Stages: Ne burning Ne-burning Main Products of Ne burning 16O, 24Mg, 28Si Scondary Products of Ne burning 29Si, 30Si, 32S

  29. Advanced Nuclear Burning Stages: Core O burning H burning shell H He He burning shell CO NeO O C burning shell Ne burning shell T~2×109 K

  30. Advanced Nuclear Burning Stages: O burning O-burning Main Products of O burning 28Si (~0.55) 32S (~0.24) Secondary Products of O burning 34S (~0.07) 36Ar (~0.02) 38Ar (~0.10) 40Ca (~0.01)

  31. 40Ca 41Ca 42Ca 43Ca 44Ca 37K 38K 39K 40K 41K 42K 35Ar 36Ar 37Ar 38Ar 39Ar 40Ar 41Ar 33Cl 34Cl 35Cl 36Cl 37Cl 38Cl 31S 32S 33S 34S 35S 36S 37S 29P 30P 31P 32P 33P 34P Proton Number (Z) 27Si 28Si 29Si 30Si 31Si 32Si 33Si 26Al 27Al 28Al Neutron Number (N) Advanced Nuclear Burning Stages: O burning During core O burning weak interactions become efficient Most efficient processes: 31S(b+)31P 30P(e-,n)30Si 33S(e-,n)33P 37Ar(e-,n)37Cl The electron fraction per nucleon

  32. Advanced Nuclear Burning Stages: Core Si burning H burning shell H He He burning shell CO NeO O C burning shell SiS Ne burning shell O burning shell T~2.5×109 K

  33. j + l i + k Advanced Nuclear Burning Stages: Si burning At Oxygen exhaustion Balance between forward and reverse (strong interaction) reactions for increasing number of processes A measure of the degree of equilibrium reached by a couple of forward and reverse processes Non equilibrium Full equilibrium

  34. At Si ignition (panel a + panel b) A=45 56Fe A=44 28Si Eq. Clusters Advanced Nuclear Burning Stages: Si burning At Oxygen exhaustion At Si ignition Sc Si Equilibrium Equilibrium Partial Eq. Out of Eq. Out of Equilibrium

  35. Advanced Nuclear Burning Stages: Si burning • 28Si is burnt through a sequence of (g,a) reactions 56Fe A=45 A=44 • The two QSE clusters reajdust on the new equilibrium abundances of the light particles 28Si 24Mg • The matter flows from the lower to the upper cluster through a sequence of non equilibirum reactions 20Ne 16O 12C Equilibrium Clusters Clusters di equilibrio 4He • Ye is continuosuly decreased by the weak interactions (out of equilibrium) 56,57,58Fe, 52,53,54Cr, 55Mn, 59Co, 62Ni NSE

  36. Pre-SuperNova Stage H burning shell H He He burning shell CO NeO O C burning shell SiS Fe Ne burning shell O burning shell T~4.0×109 K Si burning shell

  37. Evolutionary Properties of the Interior H burning shell Ne burning shell He burning shell O burning shell C burning shell Si burning shell

  38. Chemical Stratification at PreSN Stage 16O,24Mg, 28Si,29Si, 30Si 14N, 13C, 17O 14N, 13C, 17O 12C, 16O 28Si,32S, 36Ar,40Ca, 34S, 38Ar 12C, 16O s-proc 20Ne,23Na, 24Mg,25Mg, 27Al, s-proc 56,57,58Fe, 52,53,54Cr, 55Mn, 59Co, 62Ni NSE Each zone keeps track of the various central or shell burnings

  39. Main Properties of the PreSN Evolution

  40. Evolution of More Massive Stars: Mass Loss O-Type: 60000 > T(K) > 33000 Wolf-Rayet : Log10(Teff) > 4.0 • WNL: 10-5< Hsup <0.4 (H burning, CNO, products) • WNE: Hsup<10-5 (No H) • WN/WC: 0.1 < X(C)/X(N) < 10 (both H and He burning products, N and C) • WC: X(C)/X(N) > 10 (He burning products)

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

  42. 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

  43. THE EVOLUTION UP TO THE IRON CORE COLLAPSE The Iron Core is mainly composed by Iron Peak Isotopes at NSE The following evolution leads to the collapse of the Iron Core: The Fe core begins to degenerate The Fe core contracts to gain the energy necessary against gravity Tc ~ 1010 K,rc ~ 1010 K Pe ~ 1028 dyne/cm2 Pi ~ 2×1026 dyne/cm2 Prad ~ 3×1025 dyne/cm2 The Chandrasekhar Mass MCh=5.85×(Ye)2 Mis reached T,r increase A strong gravitational contraction begins enuc lowers becaus the matter is at NSE The Fermi energy increasesthe electron captures on both the free and bound protons incease as well The gravitational collapse begins The main source of pressure against gravity (electron Pressure) lowers

  44. n diffusion n n n n Neutrino Trapping Shock wave Eenergy Losses 2 x 1051 erg/0.1M Fe Core Stalled Shock n n n n n n n n Core Bounce and Rebounce “Prompt”shocks eventually stall! Fe Core n n n-sphere n n

  45. Strong Shock vs Weak Shock A strong shock propagates. Matter is ejected. A weak shock stalls. Matter falls back.

  46. Neutrino-driven explosions Stalled Shock RS=200-300 Km Energy deposition behind the stalled shock wave due to neutrino interactions: n heating n diffusion p,n n cooling n n diffusion Shock Wave reheated e+,e- n,p n Explosion n Gain Radius RG=100-150 Km Neutrinosphere Rn=50-700 Km

  47. Explosive Nucleosynthesis Propatagiont of the shock wave through the envelope Compression and Heating Explosive Nucleosynthesis Explosion Mechanism Still Uncertain 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

  48. Matter Ejected into the ISM Ekin1051 erg Induced Shock Compression and Heating Matter Falling Back Induced Expansion and Explosion Mass Cut Initial Remnant Final Remnant Initial Remnant Injected Energy Induced Explosion and Fallback

  49. Composition of the ejecta The Iron Peak elements are those mostly affected by the properties of the explosion, in particular the amount of Fallback.

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

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