# Presentation: 620214

## Evolution of Pop III 

**Evolution of Pop III **
**and very metal poor massive stars**

**Georges Meynet**
**Geneva Observatory**

**In collaboration with Sylvia Ekström, André Maeder (Geneva)**
**                                     ****Raphael Hirshi (Keele)**
**                                     ****Cristina Chiappini (Geneva-Trieste)**
**                                     ****Cyril Georgy (Geneva)**

## INSTABILITIES IN THE INTERIOR

**Dominiciano de Souza et al. 2003**

**INSTABILITIES IN THE INTERIOR**

**DEFORMATION**

**MASS LOSS**

**Kippenhahn & Thomas 1970**

**Meynet & Maeder, A&A 321, 465 (1997)**

**Zahn 1992**

**Maeder & Zahn 1998**

**Meridional circulation**

**Shear instabilities**

**Maeder & Meynet, A&A 361, 159 (2000)**

## ROTATION AND MASS LOSS

_**Radiatively driven stellar winds**_

_**Mechanical winds**_

- Increase of mass loss

- Anisotropies (fast rotation)

- Surface enrichments

- Reaching of the critical or break-up limit

**Maeder & Meynet 2000**

**Owocki, 1996; Maeder, 1999**

**Ekstroem et al. submitted**

**Meynet et al. 2006**
**Hirschi 2007**

## M, Z, Vrot

**M, Z, V****rot**

**Mixing**

- Increases when

**M**

- increases

**Z**

- decreases

**V****rot**

- increases

**Mass loss**

- At solar and higher metallicity normal radiative stellar winds

**At very low metallicity******** break-up limit & surface enrichment**

## EVOLUTION AT Z=0

**EVOLUTION AT Z=0**

- Rotating track

- Vini=0 km/s

**Ekström et al., in preparation**

- Vini/Vcrit

- 0.48

- 0.52

- 0.56

- 0.63

- 0.72

- 0.54

- Vini

- 800km/s

- 800km/s

- 800km/s

- 800km/s

- 800km/s

- 500km/s

## Mass Loss @ Z=0 due to critical limit

**Ekstroem et al. 2006**

- Stars reach the critical velocity

- (except 9 Msol model)

-  Up to 10% lost (200 Msol)

- For a given Vini, mass lost
-     increases with Z

- 60 Msol   Vini = 800 km s-1

- Z=0            :  2.4 Msol

- Z=0.00001:  6.1 Msol

- Z=0.00050:  21 Msol

**Rich in H-burning products only******** chemical anomalies **
**in Globular Clusters, Decressin et al. 2006**

## Ekstroem et al. 2006

**Ekstroem et al. 2006**

## PRIMARY NITROGEN PRODUCTION

- Mass of 14N=0.14 Msol

- Mass of 14N=0.0005 Msol

- 60 Msol

**Z=0**

- Vini=800km/s

- Vini/Vcrit=0.5

- 60 Msol

**Z=0.00001**

- Vini=800km/s

- Vini/Vcrit=0.7

## 60 Msol

**Similar extension**
**towards the red**

- Red: Z=0.00001

- Blue: Z=0.

**60 M****sol**

**V****ini****=800 km/s**

- Blue: Z=0

- Red: Z=0.00001

## Why redwards evolution not favored when Z = 0?

- No CNO element
- Temperature H-burning~Temperature He-burning 
- End MS phase, smooth transition into core He-burning
- No contraction of the core
- No redwards evolution
- Less efficient production of primary nitrogen

**Another consequence**

- No deep convective zone in the zone
- No very important CNO enhancement at that stage
- No important opacity enhancement
- No important enhancement of radiatively driven stellar winds

## 60 Msol

**V****ini**** = 0 km/s**

**V****ini**** = 800 km/s**

**14****N**

**16****O**

**12****C**

**60 M****sol**
**[Fe/H]=-6.6**

##       Theory

**Meynet et al. 2006; Hirschi 2006**

**Observations**
- Frebel et al 04,06 (stars)
- Plez & Cohen 05 (triangle),
- Aoki et al 05
- Christlieb et al 04,
- Norris et al 04,
- Depagne et al 02

-       **Theory**
- Limongi et al 2003
- Umeda & Nomoto 2003
- Suda et al 2004

## 7 Msol , Z=0.00001, Vini=800 km s-1

**Meynet, Ekström, Maeder  (2006)**

- Schuler’s talk

**7 M****sol**** , Z=0.00001, V****ini****=800 km s****-1**

## Metallicity, like the salt of the cosmos

**CONCLUSION **

- Effects of rotation on Pop III stars significant but less extreme
-     than in very metal poor stars

-  A tiny amount of metals (Z=10-8) makes a big difference

-  Rotation is a key parameter for very metal poor stars

##  ``Spinstars’’ at low metallicities?

** ****``Spinstars’’ at low metallicities?**

- Abundance anomalies
- In globular clusters
- (Li,C,N,O,F, Na,Mg,Al)

**Decressin et al 2007**

- Helium-rich stars in
- Globular clusters

**Maeder & Meynet 2007**

- High N/O in very metal poor halo stars requires rapid rotators

**Chiappini et al. 2005, 2006ab**

- C-rich ultra-metal poor stars
- might be explained if formed
- from envelope of  rapid
- rotating stars

**Meynet et al. 2006;Hirschi 2006**

- Stars at the critical limit

- Composition of stars in
- globular clusters

- Early chemical evolution
- of galaxies

- Observation
- more Be
- stars at low Z
- Theory
- more rapid
- Rotators at low Z

**Maeder et al. 1999**
**Ekstroem et al. **
**submitted**