Velocity Evolution and the Intrinsic Color of Type Ia Supernovae

Understand

To understand how best to use observations of Type Ia supernovae (SNe Ia) to obtain precise and accurate distances, we investigate the relations between spectra of SNe Ia and their intrinsic colors.

• Using a sample of 1630 optical spectra of 255 SNe, based primarily on data from the CfA Supernova Program, we examine how the velocity evolution and line strengths of Si II 6355 and Ca II H&K are related to the B-V color at peak brightness.
• We find that the maximum-light velocity of Si II 6355 and Ca II H&K and the maximum-light pseudo-equivalent width of Si II 6355 are correlated with intrinsic color, with intrinsic color having a linear relation with the Si II 6355 measurements.
• Ca II H&K does not have a linear relation with intrinsic color, but lower-velocity SNe tend to be intrinsically bluer.