Supernova Polarization Signals From the Interaction with a Dense Circumstellar Disk

TL;DR

This study models how supernova ejecta interacting with aspherical circumstellar disks produce distinctive polarization signals, revealing insights into the geometry and mass loss of progenitor stars.

Contribution

It introduces a detailed polarization model for supernova interactions with disk-like CSM, highlighting the potential for polarization as a diagnostic tool.

Findings

High polarization (~15%) from thin, disk-like CSM interaction.

Double-peaked polarization evolution linked to geometry and flux ratios.

Wavelength-dependent polarization due to temperature gradients.

Abstract

There is increasing evidence that massive stars may exhibit an enhanced mass loss shortly before their termination explosion. Some of them also indicate the enhancement of their circumstellar matter (CSM) is not spherically symmetric. Supernova (SN) interacting with aspherical CSM could induce special polarization signals from multiple radiation components that deviate from spherical symmetry. We investigate the time-evolution of the continuum polarization induced by the SN ejecta interacting with a disk/torus-like CSM. Our calculation suggests that the interaction between the SN ejecta and an immediate disk-like CSM with a thin, homogenous density structure would produce a high continuum polarization, which may reach a peak level of $\sim$15\%. The interplay between the evolving geometry of the emitting regions and the time-variant flux ratio between the polar ejecta and the equatorial CSM interaction may produce a double-peaked feature in the polarization time sequence. A similar trend of the time evolution of the polarization is also found for a radially extended CSM disk that exhibits a wind-like density structure, with an overall relatively lower level of continuum polarization ($<2.5\%$) during the interaction process. We also identify a non-uniform temperature distribution along the radial direction of the CSM disk, which yields a strong wavelength dependence of the continuum polarization. These signatures provide a unique geometric diagnostic to explore the interaction process and the associated extreme mass loss of the progenitors of interacting transients.