1. SNLS-03D3bb Andy Howell University of Toronto and the Supernova Legacy Survey (SNLS)

2. Host z = 0.2440 HST CFHT From PEGASE 2 fits to host ugriz photometry: M  yr -1  Formally implies host age of 0.7 Gyr, though highly uncertain

5. Si II velocity Low-z data from Benetti et al. 2005

6. Lightcurve V=20.5 ± 0.06 M V = -19.94 ± 0.06 Use only r, i fit s = 1.13 Sparse LC from early days of survey

7. V magnitude distribution M V = -19.94 ± 0.06 Low-z Astier et al. sample 2.2 times the luminosity of median SN Ia

8. 56 Ni mass erg s -1 M  -1 Arnett’s rule: Luminosity at maximum is proportional to spontaneous energy deposition by radioactive decay.  : ratio of bolometric to radioactivity luminosities : energy per second per solar mass from radioactive deacay Using t r = -19.5 (Conley et al. 2006),  = 1.2 (Nugent et al. 1996), get M Ni = 1.29 ± 0.07 M 

10. Velocity from kinetic energy Energy from burning to Fe peak: erg s -1 M  -1 3 kinds of elements: Fe-peak, IME, unburned C/O KE is nuclear energy minus binding energy Burning to Si produces 76% as much 56 Ni is 70% of Fe-peak elements: Binding energy (Yoon & Langer 2005) - 1.4 M  WD: 0.5e51 erg - 2.0 M  WD: 1.3e51 erg

11. Implications - Progenitors Double degenerate model: merger of two massive WDs can produce super- Chandra product. In youngest populations, only massive WDs exist. Before 0.9 Gyr, combined WD mass must be > Chandrasekhar mass. Single degenerate model: rapid rotation could support 2 solar mass WD according to Yoon & Langer 2005. Young pop. favored for higher starting WD, secondary masses.

12. Implications The most luminous SNe occur in young populations Super-Chandra model predicts more luminous SNe in younger populations Chandra model has no explanation for this. Could WD mass partially drive luminosity fluctuations in SNe Ia?

13. Conclusions - Observations M V =19.94 ± 0.06, brightest SN Ia ever observed (with the possible exception of the interacting SN 2002ic) SiII velocity at +2d among the lowest seen, 8000 km/s SiII strong relative to CaII at +2d, in contrast with other SNe Ia CII near maximum implies the presence of unburned material deep into the SN Low-mass, blue host implies a young progenitor age

14. Conclusions - Interpretation Arnett’s law implies ~1.3 M  56 Ni. If ~40% of elements are non- 56 Ni, M WD ~ 2.1 M  High 56 Ni mass implies large nuclear energy, which should produce large velocities in Chandrasekhar model. Low velocity consistent with increased binding energy of super-Chandra model. Young galaxy consistent with expectations from Super-Chandra model SNLS-03D3bb meets every expectation of the super- Chandra model

15. Conclusions - Cosmology WD mass may partially drive SN Ia luminosity SNLS-03D3bb does not follow stretch- luminosity relationship (it is too bright by 4.4 sigma). “Evolution” in SNe with redshift? SNLS-03D3bb was thrown out of Astier et al. (2006), but less extreme examples could be in data set.

16. Time to evolve off main sequence

17. What mass WD does a star make? Ferrario et al. 2005

19. UV – metallicity effects?

20. Velocity vs. WD mass

21. B-V color

22. V-R color