1. The Formation Efficiency of SNe-Ia: Single-Star Progenitors?
Dan Maoz

2. Yungelson & Livio (2000)

3. Problems with the standard scenarios DD:
merger leads to core-collapse, not Ia? (Nomoto & Iben 1985, Guerrero+ 2004, but Piersanti+ 2003)
~0/1000 binary WDs that will merge within t0? (Napiwotzki+ 2004, Nelemans+ 2005)
SD:
Fine tuning required to regulate accretion a la Hachisu+? (Piersanti+ 2000)
Wind signatures in 0/7 SN-Ia remnants (Badenes+ 2007)
SNe-Ia seen in low-metallicity galaxies, counter to Kobayashi prediction (Prieto+ 2007)
CSM found in only 1 SN-Ia (2006X, Patat+ 2007, but see Crotts & Yourdon 2008), not others
No clear ID of remaining companion in Tycho (Ruiz-Lapuente+ 2004, Fuhrman 2005, Ihara+ 2007)

4. (Mannucci et al. 2005)
SN-Ia rate is proportional to star-formation rate!

5. If “prompt” SNe-Ia explode within 100 Myr:
400
then
Primary star must be >5 Msun
>3

6. What fraction of all stars with minit=3(5)-8 Msun go SN-Ia?

7. ~1/3
~1/3 ~1
M / Msun
F(m)

8. ~ 15-30%
~(1-2)x10-3
SN-Ia/Msun
e.g. Dilday et al. 2008
~150
Msun

9. Iron in clusters (ICM+stars) easy to detect and to deduce total iron mass.
Balestra et al. (2007) Maughan et al. (2008)
Iron yields of individual SNe known directly from observations (e.g., Mazzali et al. 2007):
SN-Ia: Y(Fe)=0.7 Msun; CC-SN: Y(Fe)= Msun

10. ~ 10-20%

11. De Plaa et al. 2007
ICM abundances: NIa/NCC ~ 1
~ 30%
abnd

12. What fraction of all stars with minit=3(5)-8 Msun go SN-Ia?
Maoz 2008

13. Maoz 2008

14. ~10-30% of all m=5-8 Msun stars explode as SNe-Ia ……but……..
÷ are in binaries;
÷ have secondaries that are not too small
÷ have close enough separations
÷ : every binary can make just 1 SN-Ia!
~100% to 1000 % of close, intermediate-mass, binaries end up as SNe-Ia !

15. Binary population synthesis predictions:
Yungelson, Tutukov, Livio: DD: only 14% of close 3-8 Msun binaries go SNIa
SD: ~1%
Han & Podsiadlowski 2004: SD MS channel: B=(1-2) x 10-4 / Msun
Hachisu RG channel: negligible

16. Could SNe-Ia have single-star progenitors?
A heretical idea:
Could SNe-Ia have single-star progenitors?
SAGB ?
K. Williams (2008)

17. C/O WD ?
O/Mg WD ?
CC-SN ?
SN 1½ ?
SN-Ia ?
“Super AGB” stars
(~5-8 M_sun)

18. Circumstantial evidence:
New class of massive WDs: “Hot DQ”
Very little H (or He) in atmosphere.
Dufour et al. (2007)

19. Circumstantial evidence:
Pauldrach et al. (2004)
PN central stars: Detailed atmosphere modeling gives M~M_chandra in 5/9 cases.
1.40 Msun
1.39 Msun

20. Circumstantial evidence:
Magrini et al. (2003): low metallicity dwarf galaxies lack PNe.
Log N(PN)/L*

21. Direct progenitor searches:
SN2006dd and SN2006mr in NGC 1316, D=19 Mpc
Maoz & Mannucci 2008

23. SN2008bk in NGC 7793, D=3.9 Mpc
Maoz & Mannucci 2008

26. Conclusions:
1. Several different observables consistently indicate a high SN-Ia formation efficiency, X expected from progenitor models.
2. Late evolution of intermediate-mass stars needs to be better understood theoretically and observationally.
3. Pre- and post-explosion searches for evolved intermediate-mass SN-Ia progenitors are feasible.