Istituto Nazionale di AstroFisica (Istituto di Astrofisica ...
Transcript of Istituto Nazionale di AstroFisica (Istituto di Astrofisica ...
The stellar yieldsAlessandro Chieffi
Istituto Nazionale di AstroFisica (Istituto di Astrofisica e Planetologia Spaziale)
Centre for Stellar and Planetary Astrophysics – Monash University - Australia
Email: [email protected]
GREAT–ESF WORKSHOP
The metallicity distribution in the Milky Way discs
(Bologna, 29-31 May 2012)
H
He
CO
Fe
ZrBa
Th
Zn
Pb
N
Li
Be
B
F
NeSi
S
Ca
Ti
Ar Ni
1H 2H
3He 4He A=5
6LiA=5 7Li
A=5
A=8
9Be
11B10B
12C
A=8
A=8
13C
A=5
A=8
A=8
A=5
A=8
N
P
H
He
CO
Fe
ZrBa
Th
Zn
Pb
N
Li
Be
B
F
NeSi
S
Ca
Ti
Ar Ni
Kr
Mo Sn
Nd
Yb
Solar chemical composition
The Coulomb barrier prevents an easy fusion between charged particles: only a combination of high temperatures, high densities and long timescales may lead to a substantial amount of fusion.
Evidence
Even the fusion of the lightest nuclei, protons, requires
T > several 106 K ρ > several grams / cm3
to burn a significant amount of nuclei on a timescale shorter than the age of the Universe
These conditions are met only in stars
M
Basic flavor of the evolution of a star
From a nucleosynthetic point of view we can consider two main classes of stars:
Intermediate mass stars &
massive stars. (+Type Ia Supernovae)
M>10 MO reach TC = 1010 K , collapse & explode
M<10 MO form an e-degenerate core, lose their envelope and end up as white dwards
T c
c∝Mlog10T c∝
13
log10 c
H
HeC/OOSi
H-burning (T~ 4·107) He-burning (T~ 1.5·108) C-burning (T~ 7·108) Ne-burning (T~ 1.2·109) O-burning (T~ 1.8·109) Si-burning (T~ 2.8·109)
Hydrostatic Evolution
Massive stars
infalling matter
outgoing shock from rebounce
proto neutron star
ATTENTION: photodisintegrations activate for 30 KT=Qi.e. T(BK) = 0.4 Q (MeV)
NSE QSE 2QSE
ScTiFeCoNi
VCrMnTiFeSiSArCa
SiSArCaK
NeNaMgAlPCl
f(ρ,T,Ye) f(ρ,T,X
i)
He burn. C shell burn.
H burn.
Expl. O burn.&
Incomplete expl. Si burn.
Expl. O burn.
Incomplete expl. Si burn.
NSE ( complete expl. Si burn.)He & C shell burn (n-capt.
nucleosynthesis)
H
He
CO
Fe
ZrBa
Th
Zn
Pb
N
Li
Be
B
F
NeSi
S
Ca
Ti
Ar Ni
Kr
Mo Sn
Nd
Yb
Solar chemical composition
M
Basic flavor of the evolution of an intermediate mass star
InertCO
core
He burning shell
Intershell He+C+s
H burning shell H rich mantle
Neutrons produced by 2 processes: 13C(α,n)16O and 22Ne(a,n)25Mg
Main characteristics:The two burning shells cannot be active simultaneously
Matter freshly synthesized in the intershell is brought to the surface
13C(α,n)16OS-process nucleosynthesis
Active H burning
Active He burning
He ignition (Thermal Pulse)
He – C rich zone
H rich zone
XP < 4x10-4
n-fluence “s” process 13C(α,n)16O
n-fluence “s” process 13C(α,n)16O
12C(p,g)13N(e+v)13CH
H
14N
14N
14N
14N
N
N
N
N
N
N
Courtesy: S. Cristallo
PHYSICS OF ROTATIONSTRUCTURE
• Oblateness (interior, surface)• New structure equations
Von Zeipel Theorem
Meridional Circulation
Local conservation Meridional circulation
Advection of angular
momentum
Increase the gradient of angular velocity
Shear Instabilities
Transport of Angular Momentum
Transport of Chemical Species
Courtesy: G. Meynet Courtesy: G. Meynet
Thank You !