1. On The Fate of a WD Highly Accreting Solar Composition Material Irit Idan 1, Nir J. Shaviv 2 and Giora Shaviv 1 1 Dept. Of Physics Technion Haifa Israel 2Racah Inst. for Theoretical Physics The Hebrew University Jerusalem, Israel Irit Idan 1, Nir J. Shaviv 2 and Giora Shaviv 1 1 Dept. Of Physics Technion Haifa Israel 2Racah Inst. for Theoretical Physics The Hebrew University Jerusalem, Israel

2. Steady burning Classical Novae Focus of the talk Nomoto et.al 1982 The Set Up: WD accreting solar materials has been studied for a long time, usually in the range of that matches Classical Novae. Above this accretion rate, no dynamic calculation (some non-dynamic calc.) but speculations and assumptions as a SN progenitors Red Giants

3. Questions Posed- Questions Posed- Does the mass of the WD increase ? If it does, will it get to the Chandrasekhar mass and become SN ? Is it a viable model for a Supernova of any type ?

4. Initial conditions: In most previous works: the accreted layer is placed on the WD ignoring gravitational energy release during the accretion process This is essential because it changes the process from adiabatic to isothermal

5. Numerical Problems The problem is awfully non linear and small time steps are needed. The burning is unstable and the details are important for the final outcome of the scenario. Many cycles are needed - one cycle doesn’t tell the whole story. All mechanisms are required: accretion, nuclear burning, expansion, mass ejecting and so on...

6. spherical C/O WD, core temperature of 10 7 K Accretion rate of Accreted material - solar composition. Up to 4000 mass grid points in the accreted envelope. A fine mass shell tuning near the WD surface and near the outer edge of the accreted envelope. Nuclear grid of 60 nuclei up to A=44 Opacities - OPAL Opacities (Iglesias & Rogers 1996) Our particular run presented here

7. getting into the steady state Accreted envelope mass “semi” outburst Luminosity variations about a factor of 10 and close to the Eddington luminosity Cycle period ∼ 7-8 years. The peak luminosity is flat, the rise very fast.

8. Nuclear Luminosity The spikes demonstrate the sensitivity of the Helium burning

9. Following the second outburst - Tmax ∼ 10 8 K. All the H is converted into He. High accretion rate high entropy (Non-degenerate), ignition at low pressure weak outbursts velocity lower than the escape velocity. The accretion builds a He layer above the core - no H is left. (Adiabatic) Tmax(t)

10. Comparison to Classical Nova Accretion rate of End/Beginning of Cycle Accretion phase until the nuclear luminosity in high Expansion of the envelope and ejection For high accretion rate - There is not enough energy in the small outbursts to eject the Helium envelope Accretion rate of

11. Cycle number Power in Lsun The fast rise is due to helium burning runaway. The H burning is not degenerate. The He is very degenerate Fast heating causes expansion and escape velocities

12. Energetic summary δ(GM/R)at the sonic point ~0.15 Enuc(H)/Enuc(He) He burning causes fast expansion and decrease in GM/R to allow helium burning to eject matter H burning gives rise to envelope expansion on its way to become a steady-burning red giant Is the result sensitive to our assumptions? We changed L boundary and adopted a more stringent mass loss algorithm and found no change in the final result

13. T Profile - end of the cycle The small outburst cause secular heating of the layer giving rise to the expansion of the envelope. C/O WD immersed in a hot degenerate Helium envelope.

14. Secular evolution of the T profile profileprofiles The temperature close to the bottom of the envelope reaches This is why the He burns

15. Finally.... After 4150 cycles ∼ 40,000 yr, The pressure and temperature in the accreted envelope are high enough for He detonation to start, and in a series of 5 consecutive outbursts the WD ejects all the accreted material. Tmax Recall energetic No increase in WD mass But No C Detonation Eventually

16. Abundances He 4 0.707 C 12 0.134 O 16 Ne Na Mg Al Si No Hydrogen in the Ejecta

17. New Physics As the radiative luminosity approaches the Eddington’s luminosity, the radiative transfer becomes unstable against condensations and macaroni-type inhomogeneities (Nir Shaviv). The major effect is blocking the radiation by the denser macaroni and allowing free radiation streaming in between. The outcome does not average to the state before.

18. But... Novae are super- Eddington Schwarz et al. 1998 L edd (M=1.4M sun X=0) L edd (M=1.0M sun X=0) Schwarz et al. 2001 L edd (M=1.4M sun X=0) L edd (M=1.2M sun X=0.3) As the observations show: The nova time scale is >> dynamic time scale. Hence, steady super- Eddignton flow

19. Next Step: Allow for Super- Eddington States Instabilities give rise to inhomogeneities, reducing the effective opacity Optically Thick wind Method: Modify  for large L/L Edd No Change in the results

20. Summary High accretion of solar composition does not lead to WD mass increase (for 1Msun WD and 1.25Msun) This is not a viable model for any kind of SN Novae exceed the Eddington luminosity for periods much longer than the dynamic time, and do not allow for increase in WD mass at high accretion rates (at low accretion rates there is WD ablation) Ejecta without any hydrogen and high Z (0.3)

21. Thanks for the attention Dana Shaviv

22. accreting He at high accretion rate

24. The steady state

25. Abundances C+O He 4 Solar comp.