Colloquium

On Variations in the Peak Luminosity
of Type Ia Supernovae

Dr. Frank Timmes
Los Alamos National Laboratory

*Tuesday, March 7, 2006   4:00 p.m.  NSH 127

(Refreshments at 1:30 p.m. NSH 124)

 

I'll explore the idea that the observed variations in the peak luminosities of Type Ia supernovae originate in part from a scatter in metallicity of the main-sequence stars that become white dwarfs. Chandrasekhar mass models of Type Ia supernovae produce most of their radioactive nickel in a thermonuclear burn to nuclear statistical equilibrium where the electron to nucleon ratio is constant. I'll show analytically that simple charge and mass conservation then constrain the mass of nickel produced to depend linearly on the original metallicity of the white dwarf progenitor. This curious result is independent of any complicated hydrodynamics or flame propagation microphysics, and recent multi-dimensional models of the explosion confirm this linear dependence. The observed scatter in the metallicity of field stars is enough to induce a 25% variation in the mass of nickel ejected by Type Ia supernova, which is enough to account for most, but not all, of the observed variations in peak luminosity. I'll suggest this contribution to the intrinsic scatter in the peak luminosity is present in spirals and elliptical galaxies out to the limiting redshifts of current observations.

*Note different day and time