Prsentation PowerPoint

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ROTATING MASSIVE STARS IMPACT ON STELLAR
POPULATIONS AND NUCLEOSYNTHESIS
Georges Meynet, André Maeder, Raphael Hirschi and
Sylvia Ekstroem
Geneva Observatory
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• PHYSICS OF ROTATION
• STRUCTURE
• Oblateness (interior, surface)
• New structure equations
• Shellular rotation
• MIXING
• Meridional circulation
• Shear instabilities diffusion
• Horizontal turbulence
• Advection diffusion of
• angular momentum
• Transport diffusion of the
• chemical elements
• MASS LOSS
• Increase of mass loss by rotation
  
• Anisotropic losses of angular

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Cells of meridional circulation
Very important process for the transport of
the angular momentum
20 Msol on the ZAMS
Outwards and inwards transport of angular
momentum
GRATTON- ÖPIK CELL
Occurs when star deformed
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Meridional circulation
Gradients of
Shear instabilities
Zahn 1992 strong horizontal turbulence,
shellular rotation
Transport of the chemical species
Transport of the angular momentum
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the radiation observed to be emitted must
work its way through the star, and if there were
too much obstruction it would blow up the star. 
 
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Frad ? geff
The Von Zeipel theorem (1924)
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STELLAR WINDS ROTATION
Maeder, 1999 cf. Owocki, 1996
iso mass loss
For stellar formation also
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Idem with Teff 25000 K
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New grids of stellar models
Also Z0.040 0.008, 0.004, 0.00001
Pop III
Meynet and Maeder 2003
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N/C grows during the MS, even for early B stars
(cf.Lyubimkov 1996) OK with B, A
supergiants (cf. Gies Lambert 1992 Lennon
1994 Venn 1998,) (cf. Maeder, 1987 Langer,
1992 .)
300 km/s
200
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WHAT CHANGES AT VERY LOW Z FOR ROTATING MODELS ?
Meridional velocities smaller
MORE ANGULAR MOMENTUM IN THE CORE
Steeper gradients of the angular velocity in the
interiors
MORE EFFICIENT MIXING
Less angular momentum removed by stellar winds
BREAK-UP LIMIT
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Gradients of ? steeper at lower metallicity
20 Msol, Xc mass fraction of H at the centre,
Vini 300 km/s
Stars more compact, transport of angular
momentum less efficient
Why ?
Consequences ?
More efficient mixing of the chemical elements
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9 Msol
When Z
Surface enrichments
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Number of stars
Max/ini N/H 40
Log (N/H)12
8.8
8.4
8.0
7.6
7.2
6.8
6.4
Max/ini N/H 8
Venn Przybilla 2003
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B/R PROBLEM Lots of RSG observed at low
Z, but current models predict none. B/R 50
Langer Maeder, 1995
Models with rotation are OK with B/R 0.50.8
in SMC cf. Maeder Meynet 2001

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Y
with rotation
With rotation - Larger core - More He in
shell - H shell less active - no intermed.
conv. zone
Mr/Msun
RSG
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CONSISTENT WITH MODELS More fast
More Rotators RSG
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NUMBER RATIOS OF MASSIVE STARSIN NEARBY
GALAXIES
GALAXY Z WR/O WC/WR RSG/WR
Conti Maeder94 Massey 02
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What are the effects of rotation on the
Wolf-Rayet star formation process ?
Hot stars ? Log Teff gt 4.0
Mass fraction of hydrogen At the surface below 0.4
In non-rotating models Mass loss the key
parameter
In rotating models Rotational diffusion and mass
loss
Maeder 1987 Fliegner and Langer 1995 Meynet and
Maeder 2003
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For a given metallicity, the minimum initial mass
of single stars which become Wolf-Rayet star is
decreased for higher rotation velocities
WR lifetimes also increased for a given initial
mass
22Msol
37Msol
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20Msol
22Msol
Mmin WNE
25Msol
40Msol
Meynet and Maeder 2004
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Meynet and Maeder 2004
Observed points from Prantzos and Boissier (2003)
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25 Msol from core H-burning to Si-burning
V0 km/s
V300 km/s
Hirschi, Meynet, Maeder, Goriely 2003
Heger, Langer, Woosley 2000
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PRIMARY NITROGEN
HII regions
Pagel 1997 Garnett 1990
Metal-poor dwarfs of the Solar neighborhood
DLA
Pettini et al 2002
Carbon et al. 1987
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A new mechanism induced by rotation
S-process ?
Cf. Herwig et al, 2003
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For Z0.004 and Z0.020 , nearly no primary N
production
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WHAT CHANGES AT VERY LOW Z FOR ROTATING MODELS ?
Meridional velocities smaller
MORE ANGULAR MOMENTUM IN THE CORE
Steeper gradients of the angular velocity in the
interiors
MORE EFFICIENT MIXING
Less angular momentum removed by stellar winds
BREAK-UP LIMIT
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Pop III stellar models
40Msol
60Msol
85 Msol
200 Msol
Mass Fraction of Hydrogen at the centre
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16O
16O
4He
4He
1H
1H
12C
14N
12C
60 Msol
25Msol
30Msol
Pop III
14N
Mco larger in the rotating model
Chemical composition of the radiative envelope
PRIMARY 13C and 14N
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New data 2004
Spite et al. 2004 Israelian et al. 2004
NEED OF IMPORTANT PRIMARY PRODUCTION BY MASSIVE
STARS
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CONSEQUENCES FOR NUCLEOSYNHESIS
rotating
Z 0.00001
Non rotating
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CONSEQUENCES FOR NUCLEOSYNHESIS
Z 0
rotating
Z 0.00001
-6.6
Non rotating
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60 Msol, Fe/H-3.3 and 6.3
Non rotating
Log Teff
Rotating
Yc
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4He
4He
14N
Yc 0.12
12C
Zsurf/Zini64
Yc 0.40
Zsurf/Zini1
16O
4He
4He
Fe/H-3.3
Yc 0.08
Zsurf/Zini392
Case for Fe/H-6.3 Very similar
Yc 0.02
Zsurf/Zini1336
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COMPOSITION OF THE WIND EJECTA
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COMPARISON WITH C-RICH EMP STARS
Christlieb et al. 2004 HE0107-5240 Fe/H-5.3
Depagne et al. 2002 CS 22949-037 Fe/H-4
Norris et al. 2001 CS 22949-037 Fe/H-4
Aoki et al. 2002 CS 29498-043 Fe/H-3.75
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COMPARISON WITH C-RICH EMP STARS
Christlieb et al. 2004 HE0107-5240 Fe/H-5.3
Depagne et al. 2002 CS 22949-037 Fe/H-4
Norris et al. 2001 CS 22949-037 Fe/H-4
Aoki et al. 2002 CS 29498-043 Fe/H-3.75
Ne
F
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Evolution f (M, Z, O, )
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ROTATING MODELS
Surface enrichements
Blue to red supergiants ratio at low metallicity
Wolf-Rayet to O-type stars at various
metallicities
Type Ibc to type II supernovae at various
metallicities
At low metallicity predict higher enrichments
higher
velocities
primary Nitrogen
very metal poor stars
Pulsar rotation rates/GRB progenitors
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EFFECTS OF ROTATION AT VERY LOW METALLICITY
ROTATIONAL MIXING
13C and 14N produced in great quantities
ROTATIONAL MASS LOSS
May loose half of their initial mass through
stellar winds
NUCLEOSYNTHESIS
Pair instability supernovae avoided ?
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A correct treatment of the transport of angular
momentum in all phases is necessary ! If so,
high final ang. momentum
Hirschi, Meynet Maeder, 2004
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Do the models reproduce the observed rotation
rate of young pulsars ?
Observed rotation periods of young pulsars 2ms
100 ms (20ms)
Middletich et al. 2000 Romani Ng 2003
Marshall et al. 2003
Pre SN
25 320 X angular momentum in young pulsars
In pre SN stages, more efficient angular
momentum Processes ?
For NS with P20ms
Loss of angular momentum during the collapse
? Fryer and Warren 2004
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Relation SN - GRB
COLLAPSAR
Woosley, 2002
Hjorth et al. 2003
Precursor Rotating WR star ? Is there enough
rotation ? 1 of all WR
would be enough.
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Conditions for a collapsar
WR
To have sufficient angular momentum
Pre SN
Zsol
? gt 1016 cm2 s-1
But No WO STARS !
For NS at break-up
Woosley 2003
To have lost its H-rich envelope, to be a WO
star (Mhe gt 8 Msol-gt BH)
For NS with P20mms
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Z 0.040
Z 0.020
Z 0.008
Z 0.004
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WR
Zsol
ZSMC
Candidates for Collapsars, reduced region at low
Z