Perturbations of SNe Ia lightcurves, colors and spectral features by circumstellar dust

TL;DR

This study uses Monte Carlo simulations to explore how circumstellar dust scattering influences Type Ia supernova lightcurves, colors, and spectral features, providing potential observational tests for the dust hypothesis.

Contribution

It demonstrates that circumstellar dust can significantly alter supernova observables and proposes specific signatures to test this hypothesis observationally.

Findings

Circumstellar dust affects lightcurve widths and color evolution.

Simulations show intrinsic color variations of 0.05-0.1 mag.

Large shells produce an excess tail in B-band lightcurves.

Abstract

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 lightcurves and spectral features. We find that the effects on the lightcurve 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=1e16-1e19 cm, the lightcurve modifications are well described by the empirical Dm_15 parameter and intrinsic color variations of order sigma_{BV}=0.05-0.1 arise naturally. For large shell radii an excess lightcurve tail is expected in B-band, as observed in e.g. SN2006X.