SNLS-03D3bb

Andy Howell

University of Toronto

and the Supernova Legacy Survey (SNLS)

Hostz =

0.2440

81.050.093.8log

galM

HST

CFHT

CFHT

From PEGASE 2 fits to host ugriz photometry:

02.01

81.050.0

26.1

93.8log

SFR

M gal

M yr-1

Formally implies host age of 0.7 Gyr, though highly uncertain

Si II velocityLow-z data from Benetti et al. 2005

LightcurveV=20.5 ± 0.06

MV = -19.94 ± 0.06

Use only r, i fit

s = 1.13

Sparse LC from early days of survey

V magnitude distribution

MV = -19.94 ± 0.06

Low-z Astier et al. sample

2.2 times the luminosity of median SN Ia

56Ni mass

)(tS

L=M

r

bolNi α

/111e101.43+

/8.8e106.31=S rt43rt43 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

S : energy per second per solar mass from radioactive deacay

Using tr = -19.5 (Conley et al. 2006), = 1.2 (Nugent et al. 1996), get MNi = 1.29 ± 0.07 M

Velocity from kinetic energy

WD

bnke M

)E(E=v

2

)f+(fME=E IMEFeWDFen 0.76

Energy from burning to Fe peak:

51101.55=EFe 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

56Ni is 70% of Fe-peak elements:

FeWDNi fMM 7.0

Binding energy (Yoon & Langer 2005)- 1.4 M WD: 0.5e51 erg- 2.0 M WD: 1.3e51 erg

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.

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?

Conclusions - Observations

• MV=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

Conclusions - Interpretation

• Arnett’s law implies ~1.3 M 56Ni.

• If ~40% of elements are non-56Ni, MWD ~ 2.1 M

• High 56Ni 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

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.