Polarization signatures of the head-on collision model for Type Ia supernovae: How much asymmetry is too much?

Abstract

In a previous paper, we showed that the asymmetric ejecta produced by (zero impact parameter) head-on collisions of carbon-oxygen white dwarfs allow these progenitor models for Type Ia supernovae (SNe Ia) to cover the observed two-dimensional (2D) distribution of Si II line depths (Branch plot). In this paper, we study the polarization signature associated with the 2D asymmetric ejecta of the collision model and a double-detonation model using similar TARDIS radiative transfer simulations along different lines of sight with a spherical photosphere, combined with a new 3D Monte Carlo polarization code. We show that the polarization $Q$ can be parametrized as a product $Q=Q_{\max }{Q}_{\mathrm{x}}$ of a radial structure component $Q_{\max }$ which is insensitive to the model specifics and is shown to be universally around $Q_{\max }\sim 5\%$, and a cancellation component $Q_{\mathrm{x}}$ which depends on the asymmetry details. The continuum polarization is found to be low for both the collision and double-detonation models with $Q\sim 0.5\%$. However, the irregular Si distribution in the 2D head-on collision model results in Si II line polarization reaching $Q\sim 3\%$ ($Q_{\mathrm{x}}\lesssim 50\%$) in tension with observations (mostly $\lesssim 1.2\%$). In contrast, we show that the double-detonation model also covers the Branch plot, and yet results in low line polarization $Q\lesssim 0.7\%$ ($Q_{\mathrm{x}}\sim 10\%$) consistent with previous results and most SNe Ia. These results strengthen the case for asymmetric explosions as progenitors of SNe Ia, emphasizing an additional requirement for large polarization cancellations to account for the low observed line polarizations.

11 pages, 15 figures

References in corpus (9)

• Double-detonation sub-Chandrasekhar supernovae: can minimum helium shell masses detonate the core?
• Spectropolarimetry of Supernovae
• The Spectroscopic Diversity of Type Ia Supernovae
• Double Detonations with Thin, Modestly Enriched Helium Layers Can Make Normal Type Ia Supernovae
• Spectropolarimetric diagnostics of thermonuclear supernova explosions
• Multi-Dimensional Parameter Study of Double Detonation Type Ia Supernovae Originating from Thin-Helium-Shell White Dwarfs
• Polarisation spectral synthesis for Type Ia supernova explosion models
• Multi-Dimensional Radiative Transfer Calculations of Double Detonations of Sub-Chandrasekhar-Mass White Dwarfs
• Predicting polarization signatures for double-detonation and delayed-detonation models of Type Ia supernovae

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• Science with a large field-of-view polarization survey: The Large Array Survey Telescope Polarization Node (LAST-P)