Discussions about Z effects on the Conti scenarioGeneva, 1983

Peter sitting on pure Z=1 materials in Arapahoe PeakBoulder, 1989

Peter during a bicycle tripGeneva 2002

Peter with some of his many disciples… Boulder, 2003

MASSIVE STARS EVOLUTION

in collaboration with :

Georges Meynet Raphael Hirschi (Univ. Keele) Patrick Eggenberger (Univ. Liege) Sylvia Ekström Cyril Georgi

MASSIVE STARS:

1.137.05.0

3.0

1~~~

~~

MR

MMR

MTR

MT

MASS LOSS :

MIXING: shear ~ thermal diffusivity

High T Low

2

3

3

4

PC

TacK Mass loss and mixing

strongly favoured !

3

~T

P

P

gas

rad

Huang & Gies (2006); see also Conti & Ebbets 1977- Peak of Vrot = 200 km/s

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

Rotation in B stars

Both effects interact:- Mass loss removes angular momentum - Rotation enhances the M- loss rates

ROTATIONAL DISTORTIONACHERNAR ~9.6 Msol

Domiciano de Souza et al. 2003 : difficulty ?Carciofi et al. 2008: equatorial disk Re/Rp=1.5

ROCHE MODEL OK for ω =0.992

pR

GMR

R

GM

rP

222

22

sin2

1

)sin(2

11

Frad geff Teff ~ geff 1/4

Von Zeipel (1924)

Confirmation of Von Zeipel

Peterson et al. 2006Monnier et al. 2007

Teff(pole)/Teff(equateur)=1.23-1.27

GRAVITY DARKENING

Altair 1.8 Msol ω =0.9

The exponent may be smaller ~0.19 Monnier, 2007

1

12

.

12

1

)(

m

eff

G

gAM

iso mass loss

Owocki 1996, Maeder, 1999

STELLAR WINDS & ROTATION

64.0

10

00030

2

06

LL

K

Enables a massive starto lose lots of mass andlittle angular momentum GRBs

ACHERNAR HAS POLAR WINDS

Meilland et al. 2007

Polar mass flux 7 10-9 Msol y-1 sr-1

Mass of the disk=4.1 10-10Msol

Mass loss=1.3 10-8 Msol/y

Disk in Keplerian rotation

Intensity map in the continuum at 2.15 micron (SIMECA code)

9.6 Msol Ve=470 km/s~91% Vcrit

(N/H) depend on - v sin i- M- age- Z, etc… SURFACE ENRICHMENTS

« The observation challenges the concept of rotational mixing » Hunter et al. 2008

Stars in extendedregions aroundN11 and NGC 2004in the LMC.

Spread in masses and ages.

Sample biased toward low v sini

One must not assume log (N/H) = f(v sini)But log (N/H) = f(v sini, M, age, Z….)

Mass effect Age effect

beginning of MS phase

end

of M

S ph

ase

MS stars between 14 and 20 MO in the list by Hunter et al. 2008

Gr I disappeared, except binarieslower 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

Galaxy: [N/H] for O-stars : ~ 0.5 up to 0.8-1.0 dex< 20 M B – dwarfs : ~ 0.5 dex> 20 M B – giants , supg. : ~0.5 -0.7 dexRef: Villamariz & Herrero ’02; Smartt ’02;Herrero’03;Venn & Przybilla03;Trundle et al.’07

LMC: [N/H] for B-supg. : ~ 0.3 - 0.8 dex< 20 M B – dwarfs : ~ 0.7- 0.9 dex B – giants, supg. : 1.1 -1.2 dex > 20 M B – giants , supg. : 1.3 dexRef: Herrero’03;Trundle et al. ’07;Hunter et al.’07

SMC: [N/H] O-stars, A-F supg. : 1.5 -1.7 dex< 20 M B – dwarfs : 1.1 dex B – giants, supg. : 1.5 dex > 20 M B – giants , supg : 1.9 dexRef: Heap & Lanz’06; Venn & Przybilla’03; Bouret et al.’03;Trundle et al.’07; Hunter et al.’07

ABUNDANCES:

Gradients of steeper at lower metallicity

20 M20 MOO

More efficient mixing of the chemical elements at lower Z MM’ 01

60 Msol, Z = 0.00001

2/3 of the Main Sequence phase spent near the break-up limit

Age in Myr

300 km/s

800 km/s

MASS LOSS DUE TO THE APPROACH OF THE BREAK-UP LIMIT

End MS

Z=10-8

Solar Z radiative M - loss

Low Z stars rotational M-loss !

14N

12C

16O

Yc= 0.40

Zsurf/Zini=1

Yc= 0.12

Zsurf/Zini=64

Yc= 0.08

Yc= 0.02

Zsurf/Zini=392 Zsurf/Zini=1336

Z=10-8

Also, ΔY/ΔZ > 70, cf. Cen Maeder & Meynet 2006

ΔY/ΔZ= 70-130

Continuous line: models at Z=10-5 (MM02)Broken line: the same with larger N yieldRed: new models with fast rotation below Z=10-5

Chiappini, Hirschi, Meynet,Ekström, Maeder., Matteucci2006Confirmed by Fabbian, Nissen, Asplund, Pettini, Ackerman 2008

Most extreme stars

Gamma-Ray Bursts (GRBs)

Massive star collapsing in a fast spinning BH

• Composition: from SNIbc (WC-WO stars)

• Rotation: J > 1016 cm2 s-1

• Statistics: ~1 GRB /1000 SN more at lower Z (up to SMC) Le Floch et al. 2003;Stanek et al. 2006

Collapsar model (Woosley 1993)

Georgy et al. 2008

Yoon & Langer 2005; cf. Maeder, 1987

GRBsDifficulty: remove M without loosing too much angular momentum

homogeneous evolution

- Homogeneous evolution. Possible, but composition not corresponding !

Avoid the redMM 2006

Anisotropic winds• keep high rotation• more M loss

Meynet & Maeder 2006 0 2 4 (106yr)

Angular momentum in the central 3 MO = 8 x 1016 cm2 s-1

while j= 1016 cm2 s-1 is the limit.

Evolution of All Stellar Generations= f (M, Z, He, mass loss, rotation, binaries, magn. field, ……)• Lifetimes, tracks

• Asteroseismology• Evolution properties Be, B[e], 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, γ- bursts, ….