Transcript Slide 1

The Formation Efficiency of SNe-Ia:
Single-Star Progenitors?
Dan Maoz
Yungelson
& Livio
(2000)
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)
(Mannucci et al. 2005)
SN-Ia rate is proportional to star-formation rate!
If “prompt” SNe-Ia explode within 100 Myr:
400
then
Primary star must be >5 Msun
>3
What fraction of all stars with minit=3(5)-8 Msun
go SN-Ia?
~1/3
~1/3
~1
F(m)
5
M / Msun
8
50
~ 15-30%
~(1-2)x10-3
~150
SN-Ia/Msun
Msun
e.g. Dilday et al. 2008
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)=0.05-0.1 Msun
~ 10-20%
De Plaa et al. 2007
ICM abundances: NIa/NCC ~ 1
abnd
~ 30%
What fraction of all stars with minit=3(5)-8 Msun
go SN-Ia?
Maoz 2008
Maoz 2008
~10-30% of all m=5-8 Msun stars explode as SNe-Ia
……but……..
÷
0.7-1
÷
0.15-0.3 have secondaries that are not too small
÷
0.25-0.5 have close enough separations
÷
0.5 :
are in binaries;
every binary can make just 1 SN-Ia!
~100% to 1000 % of close, intermediate-mass, binaries
end up as SNe-Ia !
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
A heretical idea:
Could SNe-Ia have single-star progenitors?
SAGB
?
K. Williams (2008)
C/O WD ?
O/Mg WD ?
“Super AGB” stars
(~5-8 M_sun)
CC-SN ?
SN 1½ ?
SN-Ia ?
Circumstantial evidence:
New class of massive WDs: “Hot DQ”
Very little H (or He) in atmosphere.
Dufour et al. (2007)
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
Log N(PN)/L*
Circumstantial evidence:
Magrini et al. (2003): low metallicity
dwarf galaxies lack PNe.
Direct progenitor searches:
SN2006dd and SN2006mr in NGC 1316, D=19 Mpc
Maoz & Mannucci 2008
SN2008bk in NGC 7793, D=3.9 Mpc
Maoz & Mannucci 2008
Conclusions:
1. Several different observables consistently indicate a
high SN-Ia formation efficiency, 10-100X 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.