paper

Light and color curve properties of type Ia supernovae: Theory vs. Observations

arXiv:1707.05350 · doi:10.3847/1538-4357/aa84b2

Abstract

We study optical light curve(LC) relations of type Ia supernovae(SNe~Ia) for their use in cosmology using high-quality photometry published by the Carnegie-Supernovae-Project (CSP-I). We revisit the classical luminosity-decline-rate () relation and the Lira-relation, as well as investigate the time evolution of the () color and , which serves as the basis of the color-stretch relation and Color-MAGnitude-Intercept-Calibrations(CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically-symmetric delayed-detonation models(DDT) producing normal-bright and subluminous SNe~Ia. Empirical LC-relations can be understood as having the same physical underpinnings: i.e. the opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some 3-4 weeks past maximum, the photosphere recedes to Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density of the WD because at higher densities more electron capture elements are produced at the expense of Ni production. This results in a spread of 0.1 mag for normal-bright and 0.7 mag in sub-luminous SNe~Ia and mag in the Lira-relation. We show why color-magnitude diagrams emphasize the transition between physical regimes, and allow to construct templates depend mostly on with little dispersion in both the CSP-I sample and our DDT-models. This allows to separate intrinsic SN~Ia variations from the interstellar reddening characterized by and . Mixing of different explosion scenarios causes a wide spread in empirical relations which may suggest one dominant scenario.

arXiv comment49 pages, 17 figures, 3 tables accepted (Original Version: 03/29/2017; revised: 6/30/2017; accepted: 8/4/2017)

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