Transcript sydney2011_limongix - Osservatorio Astronomico di Roma

EVOLUTIONARY PATH TOWARD THE CORE
COLLAPSE SUPERNOVA EXPLOSION
Marco Limongi
INAF – Osservatorio Astronomico di Roma, ITALY
Institute for the Physics and Mathematics of the Universe, JAPAN
[email protected]
and
Alessandro Chieffi
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, Italy
[email protected]
OVERVIEW OF MASSIVE STARS PRESUPERNOVA EVOLUTION
Grid of models: 13, 15, 20, 25, 30, 40, 60, 80 and 120 M
Initial Solar Composition (Asplund et al. 2009)
All models computed with the FRANEC (Frascati RAphson Newton Evolutionary Code) 6.0
Major improvements compared to the release 4.0 (Limongi & Chieffi 2003) and 5.0 (Limongi & Chieffi 2006)
- FULL COUPLING of: Physical Structure - Nuclear Burning - Chemical Mixing
(convection, semiconvection, rotation)
- INCLUSION OF ROTATION:
- Conservative rotation law
- Transport of Angular Momentum (Advection/Diffusion)
- Coupling of Rotation and Mass Loss
- TWO NUCLEAR NETWORKS:
- 163 isotopes (448 reactions) H/He Burning
- 282 isotopes (2928 reactions) Advanced Burning
- MASS LOSS:
- OB: Vink et al. 2000,2001
- RSG: de Jager 1988+Van Loon 2005 (Dust driven wind)
- WR: Nugis & Lamers 2000/Langer 1989
MASSIVE STARS: CORE H BURNING
Convective Core
g
g
g
CNO
Cycle
g
g
g
g
g
Core H burning
models
WNL
WNL
MASSIVE STARS: CORE He BURNING
3a+ 12C(a,g)16O
g
g
He
Convectiv
e Core
g
WR
g
g
Core He
burning models
Core He
burning models
Core H burning
models
g
H burning shell
g
gH exhausted core
(He Core)
The location of a core He burning star
in the HR diagram depends on the mass
of its H envelope.
The Mass Loss rate during the RSG phase is
crucial in determining if and when (at which
stage of core He burning) such a transition
occurs and if and when the star enters the
Wolf-Rayet stage or becomes a YSG
WNL
WNL
WNE
WNC
WC
WNE
WNC
WC
WNL
WNL
WNE
WNC
WC
WNE
WNC
WC
EVOLUTION DURING H AND He BURNING: SUMMARY
Initia
l
Mass
Final
Mass
MH
MHe
Progenitor
SN
13
12.0
5.46
4.49
RSG
II-P
15
13.4
5.75
4.90
RSG
II-P
20
8.1
0.25
3.81
RSG
IIb
25
10.4
0.14
4.42
YSG
IIb
30
12.6
0.03
4.35
YSG
IIb/Ib
40
16.0
0.00
4.22
WNE
Ib/c
60
16.8
0.00
0.93
WC
Ib/c
80
22.6
0.00
1.07
WC
Ib/c
120
30.8
0.00
1.02
WC
Ib/c
Compatible with recent observational
estimates (Smartt et al. 2009):
Compatible with the observed rates
(Cappellaro & Turatto 99)
Live a substantial fraction of time as RSG and explode as as IIb/Ib
 solve the RSG problem (Smartt et al. 2009)
COMPARISON WITH WOLF-RAYET STARS POPULATION
Constant SF + Salpeter IMF
- Too few WR-stars predicted compared to O-type stars
- WNC/WR in good agreement with observations
(semiconvection during core He burning) – MM03
claimed that such an agreement could be achieved
only with the inclusion of rotation
- Too many WN predicted compared to WCO
- WR predicted masses higher than the observed ones
MASSIVE STARS: NEUTRINO LOSSES
Neutrino losses play a dominant role in the evolution of a massive star beyond core He burning
The Nuclear Luminosity (Lnuc) closely follows the energy losses
Each burning stage gives about the same Enuc
Enuc
L
M
tnuc
Evolutionary times of the advanced
burning stages reduce dramatically
tnuc  Enuc
M
L
Surface properties (Mass Loss, Teff, L) do
not change anymore till the explosion
ADVANCED BURNING STAGES: INTERNAL EVOLUTION
Four major burnings, i.e., carbon, neon, oxygen and silicon.
He
C
C
O
O
C
H
He
C
Ne O
Si
Si
Central burning  formation of a convective core
Central exhaustion  shell burning  convective shell
Local exhaustion  shell burning shifts outward in mass
 convective shell
ADVANCED BURNING STAGES: INTERNAL EVOLUTION
The details of this behavior (number, timing, mass extension and overlap of
convective shells) is mainly driven by the CO core mass and by its chemical
composition (12C, 16O)
CO core mass
Thermodynamic history
12C, 16O
Basic fuel for all the nuclear burning
stages after core He burning
At core He exhaustion both the mass and the composition of the CO core scale
with the initial mass…
ADVANCED BURNING STAGES: INTERNAL EVOLUTION
...hence, the evolutionary behavior scales as well
He
He
C
O
C
O
C
H
He
C
Ne O
Si
C
Si
H
He
Ne O
O
Si
Si
In general, one to four carbon convective shells and one to three convective shell
episodes for each of the neon, oxygen and silicon burnings occur.
The number of C convective shells decreases as the mass of the CO core increases
(not the total mass!) or asthe 12C left over by core He burning decreases.
PRESUPERNOVA STAR
…and also the density structure of the star at the presupernova stage
The final Fe core Masses range between:
MFe=1.14-1.80 M
In general the higher is the mass of the CO core (the lower is the 12C left over by
the core He burning), the more compact is the structure at the presupernova stage
PRESUPERNOVA STAR
The complex interplay among the shell nuclear burnings and the timing of the convective
zones determines in a direct way the final distribution of the chemical composition. The
mass loss history (RSG/WR) determines in a direct way the kind of CCSN
INDUCED EXPLOSION AND FALLBACK
Different ways of inducing the
explosion
Shock Wave
Compression and
Heating
Induced
Expansion
and
Explosion
Initial
Remnant
• Piston (Woosley & Weaver)
• Thermal Bomb (Nomoto & Umeda)
• Kinetic Bomb (Chieffi & Limongi)
Matter
Falling Back
Matter Ejected into the
ISM
Ekin1051 erg
Mass Cut
Initial
Remnant
Final Remnant
Fe core
FB depends on the binding energy: the higher is the initial mass the
higher is the binding energy
THE FINAL FATE OF A MASSIVE STAR
Hydrodynamic models based on induced explosions
Thorsett & Chakrabarty (1999)
No (or very few) bright SNIb/c predicted
No neutron stars formed by massive progenitors (contrary to recent
observational evidences, see Smartt et al. 2009)
SUMMARY
Maximum mass evolving as a RSG on a
substantial fraction of core He burning
Mmax,RSG ~ 35 M
- Consistent with the maximum luminosity of galactic RSG stars
The minimum masses for the formation of the
various kind of Wolf-Rayet stars are:
MWNL ~ 23 M
MWNE ~ 35 M
MWC ~ 45 M
- WR/O significanlty underestimated compared to observations
- WNC/WR in good agreement with observations
- Too many WN predicted compared to WCO
- WR predicted masses higher than the observed ones
RSG/YSG/BSG SNe as a function of the
initial mass
M ≤ 22 M  RSG-SN
22 M < M ≤ 35 M  YSG-SN
35 M < M  BSG-SN
SUMMARY
Maximum mass for SNII-P
Mmax,IIP ~ 17 M
- Consistent with the recent observational estimates (Smartt et al. 2009)
MSNII/SNIbc ~ 35 M
Minimum mass for SNIb/c:
In principle compatible with the observed rates
The final Fe core Masses range
between:
MFe=1.14-1.80 M
The limiting mass between NS and BH froming SNe :
MNS/BH ~ 22 M
in agreement with
Because of the large fallback No (or very few) bright SNIb/c predicted
- Large uncertainties in treatment of the fallback
- Mixing and Fallback (Umeda & Nomoto)
- Larger energies / Binary channel
PHYSICS OF ROTATION
STRUCTURE
• Oblateness (interior, surface)
• New structure equations
Meridional Circulation
Von Zeipel
Theorem
G. Meynet
Local conservation
Meridional circulation
Advection of
angular
momentum
Increase the
gradient of
angular velocity
Transport of Angular Momentum
Transport of Chemical Species
G. Meynet
Shear
Instabilities
ROTATING MODELS
THE EFFECT OF ROTATION
- Progressive reduction of the effective gravity from the pole to the equator
- Mixing of core nuclear burning products outward and fresh material inward
- Different path in the HRD diagram
- Increase of the nuclear burning lifetimes
- Increase of the mean molecular weight of the envelope
- Different mass loss history
- Early entrance in the WR phase  Different mass limits and lifetimes for the
various WR stages
THE EFFECT OF ROTATION
- Progressive reduction of the effective gravity from the pole to the equator
- Mixing of core nuclear burning products outward and pristine material inward
- Different path in the HRD diagram
- Increase of the nuclear burning lifetimes
- Different mass loss history
- Early entrance in the WR phase  Different mass limits and lifetimes for the
various WR stages
No Rotation
Rotation
Mmin(WNL)
23
17
Mmin(WNE)
35
100
Mmin(WNC)
50
17
Mmin(WCO)
45
35
THE EFFECT OF ROTATION
- Good fit to WR/O
- Discrepancies between predicted and observed WR ratios
- Good fit to the WR luminosities
THE EFFECT OF ROTATION
NO ROTATION
Initia
l
Mass
Final
Mass
MH
MHe
WITH ROTATION
Progenitor
SN
Initia
l
Mass
Final
Mass
MH
MHe
Progenitor
SN
13
12.0
5.46
4.49
RSG
II-P
13
9.54
3.16
2.75
RSG
II-P
15
13.4
5.75
4.90
RSG
II-P
15
8.44
1.76
2.15
RSG
II-P
20
8.1
0.25
3.81
RSG
IIb
20
7.39
0.00
0.74
WNC
Ib
25
10.4
0.14
4.42
YSG
IIb
25
9.25
0.00
0.75
WNC
Ib
30
12.6
0.03
4.35
YSG
IIb/Ib
30
11.8
0.00
0.78
WNC
Ib
40
16.0
0.00
4.22
WNE
Ib/c
40
14.2
0.00
0.57
WC
Ib/c
60
16.8
0.00
0.93
WC
Ib/c
60
18.6
0.00
0.45
WC
Ib/c
80
22.6
0.00
1.07
WC
Ib/c
80
22.5
0.00
0.45
WC
Ib/c
120
30.8
0.00
1.02
WC
Ib/c
120
22.5
0.00
0.63
WC
Ib/c
OK
OK
OK
Too many SNIb/c
predicted
ROTATING MODELS
Rotational mixing during core He burning brings continuously fresh He from the
outer zones into the convective core
substantial reduction of the 12C mass fraction left over by core He burning
especially in the less massive stars where this mechanism is more efficient due to
their higher He burning lifetimes (80-120 are exceptions)
ROTATING MODELS
....hence the behavior of any given rotating star during the more advanced burning stages
will resemble that of a non rotating star having a higher mass (80-120 exceptions)
rotating models appear much more compact compared to the non rotating ones
the iron cores are larger as well and range between
MFe=1.7-2.3 M
THE FINAL FATE OF ROTATING MODELS
Hydrodynamic models based on induced explosions
Substantially larger than the observed value
Bright SNIb/c produced by rapid rotation?
No neutron stars formed by massive progenitors (contrary to recent
observational evidences, see Smartt et al. 2009)
EVOLUTION OF THE ANGULAR MOMENTUM
During core H burning the angular momentum transport is dominated by the meridional
circulation and by mass loss – the relative efficiency depending on the initial mass
From Core He exhaustion onward the evolution of the angular momentum is
dominated by the local conservation and by the convective mixing
IMPLICATIONS FOR YOUNG PULSARS AND GRBs
If the hydrodynamical simulations are wrong and we assume that all the stars would collapse
to a NS with a mass corresponding roughly to the Iron Core Mass and a Radius of 12 Km
These models have even much more angular momentum in the collapsing iron
core than a neutron star can possibly carry
Treatment of angular momentum transport still highly uncertain
(advection/diffusion, transport mechanisms and their efficiency)  should
be revised
Important the role of magnetic field (see Heger et al. 2005)
IMPLICATIONS FOR YOUNG PULSARS AND GRBs
If the large angular momenta obtained for the iron cores in this work may pose
a problem for pulsars, they are very favorable for the GRBs
minimum value needed to make a long GRB by
magnetar or collapsar formation (Burrows et al. 2007)
These models imply that all WR stars can retain enough angular momentum to produce GRBs,
either by magnetar or collapsar formation depending on the final mass. This gives a nearly
1000 times higher ratio of GRBs to SNe than the observationally implied value.
SUMMARY
The inclusion of a more efficient mass loss during the RSG phase (dust driven wind)
lowers the maximum mass for SN-IIP from ~ 30 M (old models) to ~ 17 M
without changing the maximum mass evolving as RSG, independent of rotation
The inclusion of rotation reduces the minimum mass that become a WR star from
~ 22 M (non rotating models) to ~ 17 M and the minimum masses for all the
various WR stages and also the minimum mass for SNIb/c from ~ 30 M (non
rotating models) to ~ 17 M
- Improve the fit to WR/O and to WR luminosities
- Discrepancies between predicted and observed WR ratios still remain
- Sharp transition from SNIIP to SNIb - too many SNIb/c predicted
Rotating models are much more compact and with larger iron cores than the non
rotating ones
- Implications for CCSN explosion simulations
- Average mass of NS remnant larger than observed
- Lowering of the MNS/BH from 22 to 14 (simulated explosion uncertain)
The angular momentum of the core of rotating models is too large:
- NS remnants rotating too fast
- GRB/SN ratio severely overestimated