Type Ia Supernovae standard candles Roger Chevalier Supernovae

Type Ia Supernovae: standard candles? Roger Chevalier

Supernovae – spectroscopic classification n n Filippenko 97 Type I – H absent Type II – H present

Light curves Filippenko 97

Late spectra Filippenko 97

Why SN Ia for cosmology? Luminous n Can occur in older stellar population; not closely tied to star forming regions n Uniform in properties n e. g. , Colgate 79

Basic interpretation (c. 1980) Thermonuclear explosion of Chandrasekhar mass (1. 4 M ) white dwarf n Not a complete detonation n No compact remnant n The white dwarf accretes in a binary system n The burning produces ~0. 6 M of 56 Ni, the decay of which powers the light curve n

n n n Nuclear fusion gives ~1051 ergs Adiabatic expansion in going from 109 cm to 1015 cm Power for radiation (~1049 ergs) provided by radioactivity

Chevalier 81

Chevalier 81

Woosley & Weaver 86

Late spectrum

Phillip’s relation (1993)

Filippenko 97 Hamuy et al. 96

n Hamuy et al. 96 Application of the Phillip’s relation

Light Curve Shape method Reiss, Press, Kirshner 96

n SCP (Supernova Cosmology Project) S. Perlmutter et al. n Used Phillip’s relation and light curve “stretch” n n HZT (Hi – z Supernova Search Team) B. Schmidt et al. n Used LCS method n

Riess et al. 2004 n SN Ia Discoveries at z>1 from the HST

Spectra n n SN type Redshift z Riess et al.

Riess et al.

Riess et al.

Riess et al.

Evolution leading to SN Ia n Single degenerate in binary (standard model) Low accretion of H – explodes and blown off n d. M/dt>10 -7 M /yr, stable accretion n d. M/dt>3 x 10 -7 M /yr, build up envelope → spiral-in? n “Hachisu” wind? n n Double degenerate Gravitational radiation drives binary evolution n But, unstable mass transfer → burning to ONe WD → accretion induced collapse n

Explosion physics n 1 -dimensional (spherical) models n n Deflagration DD – delayed detonation PDD – pulsating delayed detonation 3 -dimensional models n Importance of Rayleigh-Taylor instability Ropke & Hillebrandt 05

Explaining the Phillips’ relation n n Travaglio et al. 05 Metallicity – more CNO → more 22 Ne → less 56 Ni Central density at time of ignition

Conclusions We do not understand evolution leading to explosion, explosion mechanism, Phillips’ relation… n But, there are no indications that the highz SNe Ia are different from nearby ones n