10) Nucleosynthesis in Supernovae - ISNAP

Nucleosynthesis in
Supernovae
• Weak interaction in collapse & shock
•The α-Process in Cooling Shock
• Origin of long-lived radioactivity
• The r-process nuclei in ν-Wind
•The p-process in Shock Front !
Isotopic abundances in meteorites
r-process abundances in old stars
suggest existence of 2 or more sites

Weak interaction during collapse phase

Effects of Nuclear
Electron Capture
during Core Collapse
The electron capture at high
densities results in lower Y e and
generates neutrino wind which is
necessary for driving the shock.
Hix, Messer, Mezzacappa, et al ‘03

Shock front simulations in terms of
electron abundance Y e and entropy S

Emergence of shock and fallback
Mass cut

Equilibrium at high T conditions
A-1
X+n
A-4
Y+ 4 He
At high temperatures equilibrium
between all reaction channels
can occur! Moreover through
these interactions Statistical equilibrium nuclei develop
equilibrium with excited abundance states ratios
since they are in equilibrium
with all other nuclei !
Y
B
G
Z , N
Z , N
Z , N
=
G
Z , N
A
X
⋅
( ρ ⋅ N )
A−1
≡ binding energy
≡ partition function
A
⎛
⋅
⎜
⎝
2
2π
⋅h
m ⋅ kT
u
⎞
⎟
⎠
3
⋅
2
( A−1)
⋅e
−
B
Z , N
kT
⋅Y
N
n
⋅Y
Z
p

Y
Z , N
Abundance conditions in equilibrium
=
G
Z , N
( ρ ⋅ N )
High ρ: massive nuclei
High T: light nuclei
Intermediate T: High
abundance for nuclei with
high binding energy.
With decline of shock
follows a change of
abundance distribution.
⋅
A
A−1
log Abundance
10
⎛
⋅
⎜
⎝
0
-5
-10
-15
2
2π
⋅h
m ⋅ kT
u
NSE in Si-Burning
n
n
⎞
⎟
⎠
3
⋅
2
α
p
( A−1)
log Abundance
10
⋅e
-20
-20
0.8 0.6 0.4 0.2 0.0 -0.2 0.8 0.6 0.4 0.2 0.0 -0.2
log T log T
10 9
9
0
-5
-10
-15
S N
kT
⋅Y
N
⋅Y
Z
p
56Ni
28Si
40Ca
24Mg
10
44Ti

Explosive burning in shock front
Initial dissociation towards p, n, 4 He
Re-association is stat. equilibrium towards 56 Ni

Dynamical Reaction Network
α-Process
Mass 5 Gap
Mass 8 Gap
r-process ?

Temperature and density in shock
Exponential
decline for
T and ρ with
shock expanding
into outer layers

Supernova shock front nucleosynthesis

Build up of N=Z nuclei from 28 Si, 44 Ti, 56 Ni up to 64 Ge

Supernova Shock Front
Complex mixing of nucleosynthesis patterns
How far up in mass does nucleosynthesis proceed?

Supernova light curve 1987 A

Galactic 56 Ni and 44 Ti
radioactivity
⎥
⎦
⎤
⎢
⎣
⎡
=
⋅
= −
Δ
=
=
=
⋅Δ
+
+
t
bol
bol
e
L
L
L
L
M
T
dt
dM
d
T
d
T
Fe
Co
e
Ni
λ
ν
β
ν
1
2
2
1
1/2
1/2
1/2
56
56
56
;
log
2.5
0.755
77.7
6.1
)
(
)
,
(

Galactic radioactivity as SN
nucleosynthesis signature
44
Ti and 60 Co radioactivity can be used to determine mass

44
Ti observations

44
Ti & 60 Co in light curve of
SN1987A

Possible consequences of high
neutrino flux in shock-front
Neutrino capture on protons
1
H(ν + ,e + )n, neutron production
which influence the reaction
path by neutron capture.

νp-process in hydrogen rich, high
neutron flux environments
On-site neutron production
through neutrino induced
interaction: 1 H(ν + ,e + )n!
By-passing waiting
point nuclei 64 Ge,
68
Se by n-capture
reactions.

Production of light p-nuclei
Production of light p-nuclei in this model depends strongly on
Y e (e - abundance)
radial position r of νp-process site
entropy S (~T/ρ) in shock