Discussions about Z effects on the Conti scenario

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Discussions about Z effects on the Conti
scenario Geneva, 1983
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Peter sitting on pure Z1 materials in Arapahoe
Peak Boulder, 1989
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Peter during a bicycle trip Geneva 2002
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Peter with some of his many disciples
Boulder, 2003
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MASSIVE STARS EVOLUTION
in collaboration with Georges
Meynet Raphael Hirschi (Univ.
Keele) Patrick Eggenberger (Univ.
Liege) Sylvia Ekström
Cyril Georgi
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MASSIVE STARS
High T Low ?
MASS LOSS MIXING
shear thermal diffusivity
Mass loss and mixing strongly favoured !
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• Both effects interact
• Mass loss removes angular momentum
• Rotation enhances the M- loss rates

• STRUCTURE
• Oblateness
• MASS LOSS
• Enhanced winds
  
• Anisotropies
• MIXING
• Meridional circul.
• Shears
• Hzt. turbulence

Rotation in B stars
Huang Gies (2006) see also Conti Ebbets
1977 - Peak of Vrot 200 km/s
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ROTATIONAL DISTORTION
ACHERNAR 9.6 Msol
Domiciano de Souza et al. 2003 difficulty ?
Carciofi et al. 2008 equatorial disk Re/Rp1.5
ROCHE MODEL OK for ? 0.992
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Von Zeipel (1924)
Frad ? geff ? Teff geff 1/4
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GRAVITY DARKENING
Altair 1.8 Msol ? 0.9
Teff(pole)/Teff(equateur)1.23-1.27
Confirmation of Von Zeipel Peterson et al.
2006 Monnier et al. 2007
The exponent may be smaller 0.19 Monnier,
2007
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STELLAR WINDS ROTATION
Owocki 1996, Maeder, 1999
Enables a massive star to lose lots of mass
and little angular momentum ? GRBs
iso mass loss
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ACHERNAR HAS POLAR WINDS
9.6 Msol
Ve470 km/s 91 Vcrit
Mass of the disk 4.1 10-10Msol
Mass loss 1.3 10-8 Msol/y
Polar mass flux 7 10-9 Msol y-1 sr-1
Disk in Keplerian rotation
Meilland et al. 2007
Intensity map in the continuum at 2.15 micron
(SIMECA code)
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• (N/H) depend on
• v sin i
• M
• age
• Z, etc

SURFACE ENRICHMENTS
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Stars in extended regions around N11 and NGC
2004 in the LMC. Spread in masses and
ages. Sample biased toward low v sini
 The observation challenges the concept of
rotational mixing 

Hunter et al. 2008
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One must not assume ?log (N/H) f(v
sini) But ?log (N/H) f(v
sini, M, age, Z.)
Mass effect
Age effect
end of MS phase
beginning of MS phase
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MS stars between 14 and 20 MO in the list by
Hunter et al. 2008
Gr I disappeared, except binaries lower M (12
MO instead of 17 MO) Gr II evolved stars

• It would be useful
• to account for
• gravity darkening
• in v sin i
• to separate gravity
• effects due to rot.
• and evolution
• in M determinations

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ABUNDANCES

• Galaxy N/H for O-stars 0.5
  up to 0.8-1.0 dex
• lt 20 M ? B dwarfs
  0.5 dex
• gt 20 M ? B giants , supg. 0.5
  -0.7 dex
• Ref Villamariz Herrero 02 Smartt
  02Herrero03Venn Przybilla03Trundle et
  al.07
• LMC N/H for B-supg. 0.3 -
  0.8 dex
• lt 20 M ? B dwarfs
  0.7- 0.9 dex
• B giants, supg.
  ? 1.1 -1.2 dex
• gt 20 M ? B giants , supg. ?
  1.3 dex
• Ref Herrero03Trundle et al. 07Hunter et
  al.07
• SMC N/H O-stars, A-F supg. 1.5 -1.7
  dex
• lt 20 M ? B dwarfs
  ? 1.1 dex
• B giants, supg.
  ? 1.5 dex
• gt 20 M ? B giants , supg ?
  1.9 dex
• Ref Heap Lanz06 Venn Przybilla03 Bouret
  et al.03Trundle et al.07 Hunter et al.07

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Gradients of ? steeper at lower metallicity
20 MO
More efficient mixing of the chemical elements
at lower Z MM
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60 Msol, Z 0.00001
2/3 of the Main Sequence phase spent near the
break-up limit
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MASS LOSS DUE TO THE APPROACH OF THE BREAK-UP
LIMIT
Z10-8
300 km/s
End MS
800 km/s
!
Solar Z ? radiative M - loss
Low Z stars ? rotational M-loss
Age in Myr
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Zsurf/Zini1
Zsurf/Zini64
14N
Yc 0.12
12C
Yc 0.40
16O
Zsurf/Zini392
Zsurf/Zini1336
Yc 0.08
Z10-8
Yc 0.02
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?Y/?Z 70-130

Also, ?Y/?Z gt 70, cf. ? Cen Maeder Meynet
2006
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Most extreme stars
Continuous line models at Z10-5
(MM02) Broken line the same with larger N
yield Red new models with fast rotation below
Z10-5 Chiappini, Hirschi, Meynet, Ekström,
Maeder., Matteucci 2006 Confirmed by Fabbian,
Nissen, Asplund, Pettini, Ackerman 2008
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Gamma-Ray Bursts (GRBs)
Collapsar model (Woosley 1993)
Massive star collapsing in a fast spinning BH

• Composition from SNIbc
  
• (WC-WO stars)
• Rotation J gt 1016 cm2 s-1
• Statistics 1 GRB /1000 SN
• more at lower Z (up to SMC)
• Le Floch et al. 2003Stanek et al. 2006

Georgy et al. 2008
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GRBs
Difficulty remove M without loosing too much
angular momentum ? homogeneous evolution
Avoid the red
MM 2006
Yoon Langer 2005 cf. Maeder, 1987
- Homogeneous evolution. Possible, but
composition not corresponding !
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• Anisotropic winds
• keep high rotation
• more M loss

0 2 4
(106yr)
Meynet Maeder 2006
Angular momentum in the central 3 MO 8 x 1016
cm2 s-1 while j 1016 cm2 s-1 is the
limit.
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Evolution of All Stellar Generations f (M, Z,
He, mass loss, rotation, binaries, magn. field,
)

• Lifetimes, tracks
• Asteroseismology
• Evolution properties Be, Be,
• LBV, WR stars in galaxies
• Nebulae
• Evolution of rotation
• Cepheid properties
• Surface abundances in massive
• stars and red giants
• Primary N
• Pre supernova stages
• Yields and nucleosynthesis
• Rotation periods of pulsars
• Final masses
• Collapsars, ?- bursts, .

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