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Supernovae of type Ia: the final fate
of low mass stars
in close bynary systems
Oscar Straniero
INAF – Oss. Astr. di Collurania (TE)
CMB
Temperature
fluctuations
(COBE
BOOMERANG
WMAP)
 High-z Team
(Brian Schmidt & co)
 Supernova
Cosmology Project
(Saul Perlmutter & co.)
0.25 mag fainter
than for an
EMPTY Universe
Fainter = Further
1
The Universe is Accelerating: qo   M   
2
Standard
Model
CMB
+
SNe
+
H0
=
LCDM model
SNe + CMB
SNe: Perlmutter et al. 1998, Riess
et al. 1998
H o to
 16.9 Gyr
71 Km s  1 Mpc 1
12.7 Gyr
10.6 Gyr
14.5"1 Gyr (Ho=63)
8.4 Gyr
SNe+WMAP+HST
13.2"0.4 Gyr (Ho=71)
Spergel et al. 2003
6.7 Gyr
13.7"0.2 Gyr
SNe Classification
II p
Type II
II L
SNe
I b (strong He)
Core
collapse of
massive
stars
I c (weak He)
Type I
I a (strong Si)
based on spectra and light curve morphology
Thermonuclear
explosion
Standard Candles
 Bright
 Supernovae Ia
 Homogeneous
 No evolutionary effects
Thermonuclear Explosion
of a CO WD
M~MChandrasekhar
L
~ 1.4 M
Light Curve
56Ni
time

56Co
56 Fe
L  MNi
Observed Relations
Riess et al. , 1997
Brighter
Slower Decline
Dimmer
Faster Decline
Maximum Brightness - Decline Relation
Phillips et al. 1996, 1999
Calibrated locally
<> = 0.17 mag
Do Supernovae change with z ??
Hints...
SN Ia rate is smaller
in Ellipticals
Cappellaro et al. 1997
SN Ia LCs Slower (brighter)
in Bluer Galaxies
Hamuy et al. , 1995, 1996
Branch et al. 1996
Back in time>>Progenitors
Younger
&
more metal-poor
Hamuy et al., 2000
Ivanov et al. 2000
The conceptually simplest model for a thermonuclear
supernova is just an analog of a runaway chemical
reaction that become explosive : a conventional bomb.
…… bombs often fail. Similarly, most models for
astrophysical bombs (Sne Ia) often fail.
…… Further, astrophysical bombs
must occur naturally and at the
correct rate: there must be a
convincing astronomical context.
The virial theorem
2
M dM
GM
  G 
 q
 3P V
r
R
M R M
q
d
 1.5
r M M
R
r
r
g
0
1
r
r
0
PM R r M
Non-degenerate
log P
4
3
2
4
2
3
r4/3
relativistic
M2
M1
r5/3
Non-relativistic
log r
MCh  5.83Ye2
if
Ye  0.5  MCh  1.457
Massive stars
and
core collapse
Limongi, Straniero &
Chieffi, 2001
 Ye  0.45  M Ch  1.18
• e-+p  n+ne (10 MeV)
• 56Fe+g  13a+4n (124
MeV)
Evolutionary track of low mass stars
PN
0.6 CO
M=1 Mu
AGB
t=10 Gyr
Remnant: CO WD
0.6 Mu
0.55 He
0.2 CO
0.6 CO
HB
RGB
WD
0.1 He
MS
Prada Moroni &
Straniero 2002
0.5 He
Stellar evolution
M<0.8 M
t1/HO
0.8<M/M<8
15 Gyrt30 Myr
0.5<Mf /M<1.1
CO WD
8<M/M<11
t.1030 Myr
Mf =1.2-1.3 M
ONeMg WD
11<M/M<100
t. 1-10 Myr
Mf =1.2-2.5 M
Fe (Ye.0.45)
collapse NS or BH
M>100 M
t#1 Myr
O (pair jnstability)
(Ye=0.5)
may or may not explode
Astrophysical Explosive Devices
Thermonuclear SNe
C or He
detonation
C-deflagration
C-delayed detonation
Gravitational collapse
WD
WD
RG
WD
Induced Core collapse
(nuclear runaway fails)
Pair instability, core collapse & O explosion
(core collapse fails)
He-detonation
Nucleosynthesis
in Thermonuclear
SNe
C-deflagration
C-delayed detonation
SNe Ia Light
Curves: mass
and metallicity
effects
Domínguez, Hoflich,
Straniero 2001
H accreting WDs
RG
MS
Most of the
accreted material
is lost during the
H-pulse:
too long time
Merging scenario:
Double degenerate systems: CO+CO
a) GWR loss
b) secondary tidal disruption
c) accretion 10-5 Myr-1
Too fast accretion
Double Degenerate CO WDs
(M=8H10-6 M yr-1)
(M=10-8 M yr-1)
Single Degenerate.
Massive WDs: the
lifting effect of
rotation
H
Dominguez, Straniero, Isern &
Tornambe’ 1996
He
CO
Double Degenerate
Angular momentum deposition & GWR
c) accretion 10-5 Myr-1 (expansion)
d
c
e
f
g
d) “critical” accretion (contraction)
---- disk
---- WD
e) tri-axial configuration and energy
loss via GWR
f) balance between ang. mom. deposition
and energy loss (steady accretion)
g) Viscous dissipation and explosion
Piersanti, Gagliardi, Iben &
Tornambe’ 2003
Our main results for SNe Ia:
Up to MMAX =0.2 mag
C/O WDs due to different MMS
correlated with vph & trise
No dependence of MMAX with initial Z
Open Problems:
 Progenitors ??  Accretion, Rotation.
 Propagation of the burning front (1D/3D) ??
 Transition density
 How stellar populations evolve with z ??
The future