# Presentation: 174861

## IS THERE A CHANCE FOR PRIMORDIAL SNeI1/2?

** ****Reimers (1975) prescription for mass loss or its variation by Schröder and Cuntz (2005) favour the formation of SNI1/2: the stellar envelopes remain relatively massive when the cores reach *****M*****Ch****.**
** ****Vassiliadis & Wood (1993) -not in the figures, favour SNI1/2 even more strongly, as primordial stars appear relatively compact.**
** ****Blöcker prescription allows the formation of SNI1/2... but only for the lowest values of ********, where ******** represents the dredge-up efficiency:**

**IS THERE A CHANCE FOR PRIMORDIAL SNeI1/2?**
**Pilar Gil-Pons, Jordi Gutiérrez & Enrique García-Berro**

***We have computed and analysed the evolution of primordial stars of ZAMS masses between 5 and 10 M**********, with and without overshooting (OV), up to the early TP-(S)AGB. The initial mass limits for the formation of CO, ONe degenerate cores and core-collapse SNe after the main central burning stages have been determined. The possible final fates of the considered stars have been explored in the frame of the existing uncertainties.***

**Our calculations yield no third dredge-up with or without OV**

***Situation at the end of the ***
***main central burning phases***

***Stars that do not become directly SNe develop ***
***the TP-(S)AGB phase as stars with larger Z***

** ****OV decreases the initial masses that form ONe cores and CC SNe about 1.5-2.0 M********.**
** ****Our calculations lead to insignificant third dredge-up during the early TP-(S)AGB. **
** ****We have explored the possible final outcome of our stars considering the effects of OV, different mass-loss prescriptions and different third dredge-up efficiencies. **
** ****The formation of SNI1/2 cannot be discarded!!!**

***3. CONCLUSIONS***

***Stellar envelopes do not get much extra pollution ***
*** ******stellar winds are weak ***
*** ******and the cores grow...***

***Our treatment of overshooting***

***1. OUR SEQUENCES:***
*** ******5 M**********<M*******<10 M*********,***** Z = 0 ***
*** ******No OV, OV***
*** ******Gil-Pons et al (2007)***

**SNI1/2: **
**how would they look like****?**

** ****Mechanism of explosion: ******** like SNeIa**
** ****But with thick H envelopes (SNII)**

***Our more massive models***

***2. EXPLORATION OF THE FINAL STAGES***

***Is there time enough for the stars to lose their envelopes bef-ore their cores reach M******Ch******?***

***Convection near the base ***
***of the H-rich envelope*********

***Effects of Overshooting (OV) during the late evolution***
** ****Both with and without OV SNI1/2 can form from initial masses of 6 *****M*********. –The calculations have been performed with ********=0.7. When ********=0.5 also the 5 *****M********* star also ends as a SNI1/2. **
***NB: These results have been obtained using and adaptation of the expressions for R and L by Izzard et al. (2004), Karakas et al. (2002). The authors are working on formulae specific for the Z=0 case!***

**SNI1/2 ******
**WD ******

***The carbon burning phase with and without OV***

**Higher degeneracy in the case of no OV: **
**more flashes and more violent**** ****	*********** ***

**Mass loss: Reimers (1975)**** **

**Mass loss: Reimers (1975)**** **

**SNI1/2 ******

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