Late-Time Supernovae Radio Re-brightening in the VAST Pilot Survey

TL;DR

This study analyzes supernovae that exhibit late-time radio re-brightening years after optical detection, revealing unexpected radio emissions that challenge standard models and demonstrating ASKAP's potential for future supernova research.

Contribution

First detection and analysis of late-time radio re-brightening in supernovae using ASKAP data, highlighting the need to revise models of supernova circumstellar environments.

Findings

8 supernovae show significant late-time radio emission

Radio brightness exceeds predictions of standard shockwave models

ASKAP survey effectively identifies late-time supernova radio activity

Abstract

We present our analysis of supernovae serendipitously found to be radio-bright several years after their optical discovery. We used recent observations from the Australian SKA Pathfinder taken as part of the pilot Variables and Slow Transients and Rapid ASKAP Continuum Survey programs. We identified 29 objects by cross-matching sources from these ASKAP observations with known core-collapse supernovae below a declination of $+40^{\circ}$ and with a redshift of $z\leq0.15$. Our results focus on eight cases that show potential late-time radio emission. These supernovae exhibit significantly greater amounts of radio emission than expected from the standard model of a single shockwave propagating through a spherical circumstellar medium, with a constant density structure produced by regular stellar mass-loss. We also discuss how we can learn from future ASKAP surveys about the circumstellar environments and emission mechanisms of supernovae that undergo late-time radio re-brightening. This pilot work tested and confirmed the potential of the Variables and Slow Transients survey to discover and study late-time supernova emission.