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##### SN1987A in LMC

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**SUPERNOVAE**J. Isern Institut de Ciències de l’Espai IEEC - CSIC SN1987A in LMC**Contents**• Introduction • Thermonuclear supernovae • Core collapse supernovae • Fireworks • Associated nucleosynthesis • The afetrmatch**És el cel inmutable?**Saturn Venus Jupiter El cel a la matinada**El firmament medieval**Ptolomeu Aristòtil**Historical supernovae**• 185 Cen mag = -2 • 1006 (Apr 30th) Lup mag = -9 • 1054 (Jul 4th) Tau mag = -6 (Crab) • 1181 (Aug 6th) Cas mag = -1 • 1572 (Nov 6th) Cas mag = -4 (Tycho) • 1604 (Oct 9th) Oph mag = -3 (Kepler) • 1680? 1667? Cas mag = 6 ? (Cas A)**SN1572**Cassiopeia Tycho Brahe Nova Stella Uraniborg**S Andromeda: August 31st 1885, visible 18 months: Hartwig**Lundmark (1920) estimated a distance of 7 x 105 lyr 1000 times brighter than ordinary novae Z Cen (1895 in NGC5353) 5 times brighter New class of novae: “super-novae” or “extragalactic novae” Andromeda galaxy - HST**Crab Nebula - SN1054 - Crab pulsar**Lundmark (1921) suggested for the first time a connection between the Crab nebula and SN1054 Zwicky & Baade (1934) proposed to distinguish among classical novae And “supernovae”**Energetics**# The kinetic energy can be obtained from the expansion velocity (vexp ~ 5000 – 10000 km/s) if the time elapsed from the moment of the explosion to the beginning of the nebular phase is known (assuming the Thomson opacity or instance: 0.2 cm2/g)**Energetics**# The energy released in photons can be obtained just integrating the light curve: Eph~ 1049 erg (Lmax ~ 10 43 erg/s ) # At maximum light SN are as bright as galaxies. LSN 1010 L # The effective temperature is 2 T # RSN 2x1015 cm SN are balls of light!**Before 1937 few quality spectra were available**• SN1937c in IC 4182, mV ~ 8.4 displayed a completely unusual spectrum (Popper 1937) • Next SN observations showed that all SN were very similar at maximum in brightness and spectral characteristics • Zwicky (1938) and Wilson (1939) proposed the use of SN as distance indicators Popper (1937) but**Walter Baade (1893-1960)**Fritz Zwicky (1898-1974) Supernovae**SNI or SN1937c like**H lines are absent SNII or SN1940c like H lines are present**Energy sources**Gamow picture of a core collapse supernovae**Explosive sources of energy**Gravitational collapse Thermonuclear explosion Neutron star Electron degenerate core {12C,16O}{56Ni} q ~ 7x1017 erg/g 1 Mo x q ~ 1051 erg K ~ 1051 erg Eem ~ 1049 erg Lmax ~ 1043 erg/s M ~ 1.4 Mo R ~ 106 cm M ~ 1.4 Mo R ~ 108-109 cm EG ~ 1053 erg K ~ 1051 erg Eem ~ 1049 erg Hoyle & Fowler (1960) Zwicky (1938)**Exploding stars**• They play a fundamental role in shaping the galaxy • They inject 1051 ergs/explosion in the form of kinetic energy per event • They trigger the formation of new stars • They accelerate cosmic rays • They power intense galactic winds that can even remove the galactic gas and kill the process of star formation • They inject several Mo of freshly synthesized chemical elements, both stable and radioactive. • They play a key role on the origin and evolution of life • They synthesize the elements necessary to build rocky planets • They synthesize the biogenic elements • They can sterilize large regions of the Galaxy**Hipòtesis bàsiques**• La rotació és negligible • Els camps magnètics són negligibles L Les estrelles són esfèriques Conservació de la massa**Pressió: ions, electrons i fotons**Equilibri hidrostàtic . I: Fs Suposem un canvi de radi en un temps característic P+dP dA dm dr El temps de resposta gravitatori serà: P Mr Tindrem equilibri sempre que: Fi Fg El terme de pressió serà: Si hi ha equilibri:**Hydrostatic Equilibrium**Characteristic times Hydrodynamic time: HD 440 -1/2 Thermal time: 107 yr Nuclear time: 109 yr**Electron degeneracy**At high densities e- are dominant If Even at T=0 electrons (and other fermions) are able to exert pressure! Zero temperature structures can exist**The virial theorem**P=2/3 e P=1/3 e Non Relativistic Particles Extremely Relativistic Particles Ei = -EG Ei = -1/2 EG During a gravitational transition from an equilibrium configuration to another one, half of the energy is radiated away and half is invested in internal energy. Relativistic stars are not bounded MCh=1.44 <2Ye>2 Mo**1H,4He**Fases de la combustió nuclear Combustió H 4He Combustió He 12C,16O 16O,20Ne,24Mg Combustió Ne Combustió C 16O,24Mg,28Si 28Si,32S... 56Fe Combustió O Combustió Si**Massive stars build an onion like**structure through a series of contractions followed by ignitions with iron in the center.**Non relativistic electrons**If electrons are non relativistic Hydrostatic equilibrium: It is always possible to find an equilibrium structure The star only needs to contract R decreases when M increases**Nuclear reactions**Virial theorem Ei E E i ~ MT E G ~ M2 R-1 T ~ M/R ~ M R-3 Each burning phase occurs at a fixed temperature ~M-2 Light stars ignite nuclear reactions at high densities Electron degeneracy can stop the nuclear burning process ~ T3 M-2 M<0.08 Mo, H is never ignited M<0.5 Mo, He is never ignited M<8-9 Mo, C is never ignited M<10-12 Mo, Ne is never ignited M>10-12 Mo, Fe cores are formed**M<0.5 Mo, form He cores**M<8-9 Mo, form C/O cores M<10-12 Mo, form O/Ne During the AGB phase they expel the outer layers and become white dwarfs These limits change in binary systems. If close enough, stars with 2.5 Mo can give He wd of ~ 0.4 Mo Massive white dwarfs form an Fe core that gradually grows with time NGC 6751 If M R EF When EF >> mec2 electrons become relativistic**Relativistic electrons**If electrons are relativistic Hydrostatic equilibrium: It is not possible to find an equilibrium structure There is not a length scale If E < 0 R < 0 The star contracts If E > 0 R > 0 The star contracts The ideal scenario for catastrophic events !**# The energy losses by electron**captures depend on the ignition density # The injected energy depends on the velocity of the burning front Nuclear energy release Electron captures He cores always explode CO cores can explode or collapse ONe cores always collapse Fe cores always collapse**M<0.8 M¤**0.8<M/M¤<8 8<M/M¤<11 11<M/M¤<100 M>100 M¤ t>1/HO 30 Myr<t< 15 Gyr 0.5<Mf /M¤<1.1 CO WD t~10-30 Myr Mf =1.2-1.3 M¤ONe WD • ~1-10 Myr Mf =1.2-2.5 M¤ Fe collapse NS/BH • ~1Myr may or may not explode**A more careful analysis shows:**# SNII, SNIb/c have never been observed in elliptical galaxies and probably never in S0 # These SN are associated to the spiral arms! Progenitors are probably massive stars**Energy Sources**# Assume that a huge amount of energy, 1051 erg, is deposited in the center of the star. # A shock is generated and matter expands: # If the enrgy of the shock is invested in kinetic energy, there is no thermal energy to power the light curve!! Available energy sources # Shock energy deposition: Eth Ekin 1/2ESN (if the envelope is large enough) # Radioactive decay 56Ni 56Co 56Fe qNi 7x1049 erg; 1/2 = 6.1 days qCo 1.5x1050 erg; 1/2 = 77.1 days #Pulsar, if present: Lpulsar 5x1038 (33ms/P)4 erg/s P is the period and 33 ms is the period of the Crab 1051erg**# The observed light curve is a compromise between the**different energy sources and the diffusion transport (the mean free path is = (kTh)-1 # Assuming the envelope is expanding with constant velocity: Renv R0 + vexpt # We see diff t-1 and h=R0/vexp # Initially the ejecta are very opaque diff >> h and the luminosity is small # As the time goes on diff h and photons start to escape. Since the input of energy decreases exponentially there is a peak in the LC # After the peak there is radiation trapped in the envelope that diffuses outwards, so L exceeds the deposition of energy # The deposition of energy is smaller than the radioactive input and L is equal to the instantaneous deposition rate From S.E. Woosley**Contardo (2001)**56Ni 56Co escape**# After 150 days the diffusion time is smaller than the**radioactive time of 56Co and the radioactive input, without delay is seen: where t is in days and L in erg/s # Notice that as the transparency to - rays increases, the LC is below the bolometric one**# The thermal energy is dominated by radiation. If the**expansion is nearly adiabatic: T R-1 # The total thermal energy Eth VT4 R-1 # If the initial structure is compact ( 108 cm), the energy decreases from 1051 erg to 1044 erg when the radius is 1015 cm # If the structure is initially extended we can assume: The thermal energy provides a luminosity plateau that depends on the initial radius**Fireworks are determined by:**The amount of radioactive elements The size and extension of the envelope surrounding the degenerate core Which are the progenitors?**Light curves (Arnett 1996)**• The strong shock produces a radiation dominated gas • Energy is equally devided into kinetic and thermal • The expansion is nearly homologous (v r) except in the very outer layers afected by shock steepening • Spherical symmetry