stars rotate throughout the universe
DESCRIPTION
Stars rotate throughout the Universe. A. Maeder & G. Meynet. Old…. … but quite topical nowadays. Star deformation due to its fast axial rotation. Link between Long GRB and Hypernova confirmed. Dominiciano de Souza et al. 2003. Hjorth et al. 2003. - PowerPoint PPT PresentationTRANSCRIPT
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Stars rotate throughout the Universe
A. Maeder & G. Meynet
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Star deformationdue to its fastaxial rotation
… but quite topical nowadays
Link betweenLong GRB and
Hypernova confirmed
Dominiciano de Souza et al. 2003
Hjorth et al. 2003
Old…
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OBSERVATIONAL EVIDENCES FOR MIXING
• Extended cluster MS Maeder, 76; Mermilliod et al. 93
• ON stars Walborn, 76, 2002; Heap & Lanz 2003
• Fast rotators with He, N excesses Lyubimkov 91-98; Daflon et al. 99, 01 Herrero et al. 92; Villamariz et al. 02
• He, N excesses in B, A, F supergiants Gies & Lambert 92; Lennon 92, 2002 Venn 95, 2002 Venn and Przybilla 2003
• Strong He, N excess in SMC supg. Venn 95, 2002
• He, N excesses in SN 1987A Fransson et al. 89
• Boron depletion in rotating B-stars Fliegner et al. 96; Venn et al. 96, 2002
• Transition WN/WC stars Langer 91; Crowther 95, 02; Morris et al. 99
• Blue/ Red supergiant ratios at various Z Langer & Maeder 96;
Maeder & Meynet 2002
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PHYSICS OF ROTATION
• Oblatness (interior, surface)• New structure equations
• Shellular rotation• Meridional circulation• Shear instabilities + diffusion• Horizontal turbulence• Advection + diffusion of angular momentum• Transport + diffusion of the chemical elements
• Increase of the mass loss by rotation• Anisotropic losses of angular momentum
Pinsonneault, Sofia,LangerTalon & ZahnHeger & WoosleyCharbonnel & PalaciosDenissenkov etc…
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STRUCTUREcf. Kippenhahn & Thomas ‘70
The equation scheme may be written with some modifications for Meynet & Maeder ‘97
)(r
SURFACE DISTORSIONS
CHANGE OFTeff
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GRATTON-
ÖPIK CELL
Cells of meridional circulation
Zahn 1992
Maeder &Zahn 1998.
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r
XDDr
rrt
X isheareff
i )(1 2
2
rDr
rrUr
rrt
rshear
42
42
2 1
5
1)(
EvolutionMeridional circulation
Shear mixingHorizontal turbulence
Gradients of
Transport of the chemical species
Transport of the angular momentum
Advection ! Diffusion !
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DR /2
7.08.1
11
MM MSmix
Pc
acTK
2
3
3
4
FOR HIGH M MIXING TIME < MS TIMESCALE
WHY MIXING IN MASSIVE STARS ?
)(
ln
ln
4)(
42
adp
adrd
d
g
HKD
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1
12
.
12
1
)(
m
eff
G
gAM
64.0
10
00030
2
06
LL
KTeff
iso massloss
WIND THEORY IN ROTATING STARS
For stellar formation also
Maeder, 1999
Short shell ejection
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van Boekel et al. 2003
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The present wind around Eta Carinae is elongatedalong a direction aligned with the HomunculusNebula
Smith et al. 2003 alsoindicate latitude dependentwind velocity, with thehighest velocities near thepoles
Support polar enhancedmass loss.
Eta Carinae should rotateat about 90% of the break-upvelocity
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Idem with Teff =25000 K
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Z=0.02
Z=0.00001More mixing at lower Z due compactness and smaller Gratton-Öpikcirculation
steeper
Meynet & Maeder 2002
Stellar winds Transport Contraction/expansion
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Maeder, Grebel, Mermilliod 1999
Is this a general trend ?What at Z = 0 ?
From 19 clusters in Galaxy, LMC & SMC
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When rotation is accounted for, the ages are found 25 % larger. Pleiades: reconcile with age from Li depletion in low M stars.
Martin et al. 1998
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B/R PROBLEM
Lots of RSG observed at low Z,
but current models predict none.
B/R ~ 50 Langer & Maeder, ‘95
Models with rotation are OK withB/R = 0.5–0.8 in SMC cf. Maeder & Meynet 2001
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with rotation
With rotation: - Larger core - More He in shell - H shell less active - no intermed. conv. zone
RSG
Y
Mr/Msun
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N/C grows during the MS, even for early B stars (Lyubimkov 1996)
OK with B, A supergiants (Gies & Lambert 1992; Lennon 1994; Venn 1998)
300 km/s
200
Z=0.020
200 km/s
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Nine of 17 O-type stars show a surface enrichment in N up to a solar level, [N]=7.92.
Heap and Lanz 2003
O-type stars in the SMC
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Venn & Przybilla 2003
Max/ini N/H =40
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9 Msol
When Z
Surfaceenrichments
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Pettini et al 2002
Metal-poor dwarfs of theSolar neighborhood
Carbon et al. 1987
HII regions
DLA
Pagel 1997 Garnett 1990
NITROGEN
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This mechanismworks best in intermediatemass stars
-steeper rotation profile- H- and He shells are closer
Z=0.00001
14 NS-processreinforced
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Increase of primary N production when rotation increases
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For Z=0.004 and Z=0.020, nearly no primary N
AT LOW Z: HUGEAMOUNTS OFPRIMARY N
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Rotating models
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Israelian et al. 2004
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HII regions from Garnett et al. 95, 97, 99 Izotov and Thuan 99 Kobulnicky and Skillman 88 Stellar data from Gustafsson et al 99 Gummersbach et al. 98 Tomkin et al 92
Log (C/O) vs 12+Log(O/H) for extragalacticHII regions and stars
From Henry et al 2000
What is the cause of the change of slope ?
Intermediate mass stars ?
High metallicity massive stars ?
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NUMBER RATIOS OF MASSIVE STARS
IN NEARBY GALAXIES
M31 0.035 0.24 0.44 1.7
6-7.5 0.029 0.21 0.55 --
7.5-9 0.020 0.104 0.48 ~1
9.5-11 0.013 0.033 0.33 --
M33 0.013 0.06 0.52 ~4
LMC 0.006 0.04 0.20 --
6822 0.005 0.02 -- 8.3
SMC 0.002 0.017 0.11 --
1613 0.002 0.02
GALAXY Z WR/O WC/WR RSG/WR
!
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Maeder 92
Weak winds (low Z)
Ejecta rich in 16O
Strong winds (high Z)
Ejecta rich in 4He and 12C
40Msol, Z=0.001
40Msol, Z=0.020
4He 12C 16O Z
4.24 0.55 6.80 9.71
4He 12C 16O Z
6.10 4.88 2.08 8.01
Z= 0.001
Z= 0.020
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More recent works favours massive stars as the sourceof carbon at high metallicity
Gustafsson et al. 1999
``Our results are consistent with carbon enrichment by superwind of metal-rich massive stars but inconsistent with a main origin of carbon in low mass stars’’
Carigi 2000
``In the solar vicinity, the increase of C/O with Z is due to massive stars alone.’’
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YIELDS with rotation and mass loss
Mass fractions ejected Hirschi et al. 2004
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Yields in 12C
Models withrotationproduce muchmore Carbon
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Prantzos 2003
Rotating massive stars ~ AGB stars, but synthetic models…
See also Carigi 2003; Chiappini et al. 2003
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Behaviour at low metallicitydepends on the mass rangenot so much on rotation
C/O versus O/H
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FINAL MASSES