The countless facets of massive stars and
their role in the evolution of the universe.
Alessandro Chieffi
Istituto Nazionale di AstroFisica (Istituto di Astrofisica e Planetologia Spaziale)
&
Centre for Stellar and Planetary Astrophysics – Monash University - Australia
Email: [email protected]
In collaboration with Marco Limongi
Workshop on Recent Developments in Astronuclear and Astroparticle Physics
ICTP – Trieste (Italy), November 19-23, 2012
TABLE OF NUCLIDES
Courtesy
Nikos Prantzos
Evidence
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.
Even the fusion of the lightest nuclei, protons, requires
T>several 106 K
r > 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
What is a Massive Star ?
It is a star that goes through all the hydrostatic burnings
from H to Si and explodes as a core collapse supernova
Log10(Tc) = 1/3 Log10(ρc) + cost(M)
M
Why are Massive Stars important
in the global evolution of the Universe?
Explode as Core Collapse Supernovae:
- Light up regions of stellar birth  induce star formation
- Production of most of the elements (those necessary to life)
- Mixing (winds and radiation) of the ISM
- Production of neutron stars and black holes
- Eject an enormous amount of energy as neutrinos and kinetic energy
Cosmology (PopIII):
- Reionization of the Universe at z>5
- Pregalactic Chemical Enrichment
High Energy Astrophysics:
- Production of long-lived radioactive isotopes: (26Al, 56Co, 57Co, 44Ti, 60Fe)
- GRB progenitors
The understanding of these stars is crucial for the interpretation of many astrophysical facts
g
m
120
m
CNO cycle
g
g
H burning
Convective core
11
m
m
g
g
m
m
120
He burning
3a + 12C(a,g)16O
g
g
Convective core
He core
11
m
g
m
H burning shell
Strong mass loss pushes a star towards the so called Wolf Rayet phase.
Wolf-Rayet star are massive stars that are losing their mass rapidly by means of a very
strong stellar wind, with speeds up to 2000 km/s. A Wolf-Rayet star loses 10-5 solar masses a
year. These stars are also very hot: their temperature are in the range of 25,000 K to 50,000
K.
WR classification
H rich mantle
WR classification
Log10(Teff)>4.0
H < 0.4
WNL
WR classification
Log10(Teff)>4.0
H absent – He & C/N<0.1
WNE
WR classification
Log10(Teff)>4.0
H absent – He & 0.1<C/N<10
WNC
WR classification
Log10(Teff)>4.0
He,C,O
WC/WO
EVOLUTION DURING H AND He BURNING: SUMMARY
Mmax, II-P ≅ 17 M
13 < M(M) < 20
O  RSG
25 < M(M) < 30
O  RSG  WNL
40 M
O  RSG  WNL, WNE
60 < M(M) < 120
O  RSG  WNL, WNE, WNC, WC
Compatible with recent observational
estimates (Smartt et al. 2009):
Compatible with the observed rates
(Cappellaro & Turatto 99)
When the central temperature raisies above 8 108 K, Carbon starts burning.
But in the mean time....
n
CO core
n
n
Central
burning
n
He core
All the advanced burnings are neutrino dominated!
Si burn
O burn
Ne burn
C burn
H
He burn
He
C
H
H burn
burn
O
Si
10,1,0.5
a(0.9)
of the NSE abundances
Energy absorbed by the changing
When T > 2 BK matter approaches
the Nuclear Statistical Equilibrium:
the chemical composition becomes
a function of T and the N/P ratio.
5,1,0.5
56Ni(.9)
10,10,0.5
a(0.2)
54Fe(0.18)
10,10,0.42
48Ca(0.48)
time
In spite of the many efforts, no successful explosion
has been obtained yet
surface
shock front
Escamotage:
Assume that the shock wave escapes the
dense core (roughly the Fe core)
Since the explosion is not obtained “naturally”
a few assumptions are unavoidable:
1) Energy deposited in the shock front
2) Time delay between c.c. and the escape
of the shock front from the Fe core
Fe core
Final kinetic energy = 1 foe (1051 erg)
56Ni
ejected = 0.1 MO
RSG
RSG+WR
BSG+WR
Type II Type I bc
BLACK HOLE
NEUTRON STAR
RSG
RSG+WR
BSG+WR
Type II Type I bc
NEUTRON STAR
BLACK HOLE
CO core
Fe core mass
Final mass
He convective shell
Outer border of the explosive burnings C convective shell
NEUTRON STAR
Sc
Ti
Fe
Co
Ni
NSE
V
Cr
Mn
Ti
Fe
Si
S
Ar
Ca
Si
S
Ar
Ca
K
Ne
Na
Mg
Al
P
Cl
QSE 2QSE
f(r,T,Ye)
f(r,T,Xi)
He burn.
C shell burn.
Expl. O burn.
&
Incomplete expl. Si burn.
NSE ( complete expl. Si burn.)
H burn.
Expl. O burn.
Incomplete expl. Si burn.
He & C shell burn (n-capt. nucleosynthesis)
Na22 2.6 Yr
Ti44 63 Yr
Sc44 3.9 h
Ni56 5.9 d
Co56 77 d
Co57 271 d
2.842 MeV
0.268 MeV
3.653 MeV
2.135 MeV
4.566 MeV
0.836 MeV
RHESSI and INTEGRAL launched in 2002
Reuven Ramaty High Energy Solar Spectroscopic Imager
INTErnational Gamma-Ray Astrophysics Laboratory
R. DIEHL Clemson 2005
R. DIEHL Clemson 2005
Astronomy with Radioactivities V
60Fe/26Al
RHESSI
0.17± 0.05
INTEGRAL
0.14± 0.03
Diehl et al. (2006 – Nature 439,5)
Astronomy with Radioactivities V
26Al
production:
H rich mantle
1) H convective core
Central H
burning
He burning shell
He core
2) C (Ne/C) conv. shell
C convective shell
CO core
(when the star is in shell Si burning)
3) Explosive Ne burning
Fe
Shock wave
Si burning shell
Total 26Al yield as a function of the initial mass
H-burn
C(C/Ne) shell
Semi secondary origin
Semi secondary origin
Explosive Ne burn.
Primary origin
The galactic 26Al
By adopting:
mup’ =11MO – MSN I I =35MO – Mtop = 120MO
dN
 km(1 x )
dm
m2
(m2 x  m1 x )
dN
m2
Nm  k 
dm  k
1
x
m1 dm
x
m
N m2  1  k 

x
1
(m2  m1 x )
m2
(m2 x 1  m1 x 1 )
dN
m2
Mm  k  m
dm  k
1
 x 1
m1 dm
m2
dN
26
Y ( Al )  k  Y 26 (m)
dm
Al
dm
m1

M ( 26Al )  Y 26
Al
 SFR
Steady
state
a Galactic Lyman continuum Luminosity QGAL= 3.5 1053 photons/s
60Fe
60Ni
58Ni
P
61Ni
production: 1) basics
62Ni
59Co
56Fe
57Fe
59Fe
58Fe
44 d
60Fe
N
Main n donor
22Ne(a,n)25Mg
Central He burning
T < 3.5 108 K
r < 107 n/cm3
rcrit = 1010 n/cm3
Central C burning
T < 109 K
r = few 107 n/cm3
rcrit = 3 1011 n/cm3
Shell He burning
T > 4 108 K
r => 6 1010 to 1012 n/cm3
Shell C burning
T > 1.3 109 K
r => 6 1011 to 2 1012 n/cm3
Shell Ne burning
T > 1.8 109 K
r => 6 1011 to 2 1012 n/cm3
The total 60Fe production
M < 60 MO
Mainly produced by the C convective shell
M > 60 MO
Mainly produced by the C convective shell (Ledoux criterion)
M > 60 MO
Mainly produced by the He convective shell (Schwarz. criterion)
Cas A as seen by IBIS – ISGRI aboard INTEGRAL at 25 - 40 KeV
Distance 3 Kpc -- 335 yr old -- Mini 30 MO Mend 16 MO
3 lines : 67.9 KeV, 78.4 KeV, 1.157 MeV
t(
44Ti
)= 59.8 yr
Observed: M(44Ti)=1.6 10-4 MO
Predicted: M(44Ti)= 3 10-5 MO
44Ti
Not produced in a normal freeze out
tcooling >> tbuild up
Produced in the a-rich freeze-out of zones
exposed to the complete explosive Si burning
tcooling << tbuild up
( 3a > 12C(a,g)16O(a,g)...NSE )
Critical phase
O.R.F.E.O. Online Repository for the Franec Evolutionary Output
WEBPAGE: http://orfeo.iasf-roma.inaf.it
Thank You!