stars rotate throughout the universe

Stars rotate throughout the Universe

A. Maeder & G. Meynet

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…

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

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…

STRUCTUREcf. Kippenhahn & Thomas ‘70

The equation scheme may be written with some modifications for Meynet & Maeder ‘97

)(r

SURFACE DISTORSIONS

CHANGE OFTeff

GRATTON-

ÖPIK CELL

Cells of meridional circulation

Zahn 1992

Maeder &Zahn 1998.

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 !

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

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

van Boekel et al. 2003

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

Idem with Teff =25000 K

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

Maeder, Grebel, Mermilliod 1999

Is this a general trend ?What at Z = 0 ?

From 19 clusters in Galaxy, LMC & SMC

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

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

with rotation

With rotation: - Larger core - More He in shell - H shell less active - no intermed. conv. zone

RSG

Y

Mr/Msun

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

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

Venn & Przybilla 2003

Max/ini N/H =40

9 Msol

When Z

Surfaceenrichments

Pettini et al 2002

Metal-poor dwarfs of theSolar neighborhood

Carbon et al. 1987

HII regions

DLA

Pagel 1997 Garnett 1990

NITROGEN

This mechanismworks best in intermediatemass stars

-steeper rotation profile- H- and He shells are closer

Z=0.00001

14 NS-processreinforced

Increase of primary N production when rotation increases

For Z=0.004 and Z=0.020, nearly no primary N

AT LOW Z: HUGEAMOUNTS OFPRIMARY N

Rotating models

Israelian et al. 2004

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 ?

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

!

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

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.’’

YIELDS with rotation and mass loss

Mass fractions ejected Hirschi et al. 2004

Yields in 12C

Models withrotationproduce muchmore Carbon

Prantzos 2003

Rotating massive stars ~ AGB stars, but synthetic models…

See also Carigi 2003; Chiappini et al. 2003

Behaviour at low metallicitydepends on the mass rangenot so much on rotation

C/O versus O/H

FINAL MASSES