Light Curves and Spectra from a Unimodal Core-Collapse SuperNova

TL;DR

This study uses radiative transfer simulations to analyze the optical and gamma-ray emission from an asymmetric core-collapse supernova, revealing how viewing angle affects observed luminosity and spectral features.

Contribution

It introduces a detailed 3D asymmetric supernova model and compares simulated light curves and spectra with observations, highlighting the impact of asymmetry on emission.

Findings

Luminosity varies by a factor of 1.36 with viewing angle.

Spectral shifts in near-IR Ca II emission depend on viewing angle.

Gamma-ray brightness is more uniform across angles than optical emission.

Abstract

To assess the effectiveness of optical emission as a probe of spatial asymmetry in core-collapse supernovae (CCSNe), we apply the radiative transfer software, \supernu, to a unimodal CCSN model. The \snsph\ radiation-hydrodynamics software was used to simulate an asymmetric explosion of a 16 M$_{\odot}$ ZAMS binary star. The ejecta has 3.36 M$_{\odot}$ with 0.024 M$_{\odot}$ of radioactive $^{56}$Ni, with unipolar asymmetry along the z-axis. For 96 discrete angular views, we find the ratio between maximum and minimum peak total luminosities is $\sim$1.36. The brightest light curves emerge from views orthogonal to the z-axis. Multigroup spectra from UV to IR are obtained. We find a shift in wavelength with viewing angle in a near-IR Ca II emission feature, consistent with Ca being mostly in the unimode. We compare emission from the grey gamma-ray transfer in \supernu\ and from the detailed gamma-ray transfer code \maverick. Relative to the optical light curves, the brightness of the gamma-ray emission is more monotonic with respect to viewing angle. UBVRI broad-band light curves are also calculated. Parallel with the unimode, the U and B bands have excess luminosity at $\gtrsim 10$ days post-explosion, due to $^{56}$Ni on the unimode. We compare our CCSN model with SN 2002ap, which is thought to have a similar ejecta morphology.