2011ApJ...735...20A

It has been suggested that multiple scattering on circumstellar dust could explain the non-standard reddening observed in the line of sight to Type Ia supernovae. In this work, we use Monte Carlo simulations to examine how the scattered light would affect the shape of optical light curves and spectral features. We find that the effects on the light curve widths, apparent time evolution of color excess, and blending of spectral features originating at different photospheric velocities should allow for tests of the circumstellar dust hypothesis on a case by case basis. Our simulations also show that for circumstellar shells with radii r = 10¹⁶-10¹⁹ cm, the light curve modifications are well described by the empirical Δm₁₅ parameter and intrinsic color variations of order σ_BV= 0.05-0.1 arise naturally. For large shell radii an excess light curve tail is expected in B-band, as observed in, e.g., SN2006X.