Sin ttulo de diapositiva

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SUPERNOVAE
J. Isern Institut de Ciències de lEspai IEEC -
CSIC
SN1987A in LMC
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Contents

• Introduction
• Thermonuclear supernovae
• Core collapse supernovae
• Fireworks
• Associated nucleosynthesis
• The afetrmatch

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És el cel inmutable?
Saturn
Venus
Jupiter
El cel a la matinada
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El firmament medieval
Ptolomeu
Aristòtil
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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)

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SN1572 Cassiopeia
Tycho Brahe
Nova Stella
Uraniborg
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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
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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
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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)
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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!
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• 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
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Supernovae
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SN1940c
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SNI or SN1937c like H lines are absent
SNII or SN1940c like H lines are present
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Energy sources
Gamow picture of a core collapse supernovae
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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)
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SN1987A neutrinos
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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

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Hipòtesis bàsiques

• La rotació és negligible
• Els camps magnètics són negligibles

L
Les estrelles són esfèriques
Conservació de la massa
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Pressió ions, electrons i fotons
Equilibri hidrostàtic . I
Fs
Suposem un canvi de radi en un temps
característic ?
PdP
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
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Hydrostatic Equilibrium
Characteristic times Hydrodynamic time
?HD? 440 ?-1/2 Thermal time 107 yr
Nuclear time 109 yr
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Electron degeneracy
At high densities e- are dominant
If
Even at T0 electrons (and other fermions) are
able to exert pressure!
Zero temperature structures can exist
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The virial theorem
P2/3 e
P1/3 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
MCh1.44 2 Mo
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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
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Massive stars build an onion like structure
through a series of contractions followed by
ignitions with iron in the center.
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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
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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
Mnever ignited Mignited M10-12
Mo, Fe cores are formed
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Nebuloses planetàries
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Mcores MDuring 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
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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 The star contracts If ?E 0 ?R 0 The star
contracts
The ideal scenario for catastrophic events !
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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
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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
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Light curves
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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
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Diehl and Timmes (1998)
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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 ?hR0/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
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56Ni
56Co
? escape
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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
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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
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Fireworks are determined by The amount of
radioactive elements The size and extension
of the envelope surrounding the degenerate core
Which are the progenitors?
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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

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Constant velocity is a good approach
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• The luminosity scale depends on
• Initial radius
• Opacity
• Energy per unit of ejected mass (vsc2)

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• Effects of heating
• Assume as before homologous expansion
• Radiative pressure is dominant
• 56Ni is present in the ejected matter and
  smoothly distributed

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Assuming that the energy input is only from Ni,
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Assume R(0) is small
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Arbitrary radii
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X1014 cm
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SNe Statistics
SN rate per unit Mass (10-11 Mo 10-2 yr (Ho/75)2
Cappellaro, Barbon, Turatto 2003
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