A diverse, overlooked population of Type Ia supernovae exhibiting mid-infrared signatures of delayed circumstellar interaction

TL;DR

This study uncovers a previously overlooked population of Type Ia supernovae exhibiting mid-infrared signatures of delayed circumstellar interaction, suggesting such phenomena are more common than optical searches indicate.

Contribution

It introduces a new all-sky mid-infrared search method that doubles the known sample of SNe Ia with delayed CSM interaction evidence, revealing its higher prevalence.

Findings

Identified 5 new SNe Ia with mid-infrared brightening indicating delayed CSM interaction.

Estimated that over 0.05% of SNe Ia show mid-infrared signatures of CSM interaction.

Detected multiple detached CSM shells containing dust at large distances from the supernovae.

Abstract

Type Ia supernovae arise from the thermonuclear explosions of white dwarfs in multiple star systems. A rare sub-class of SNe Ia exhibit signatures of interaction with circumstellar material (CSM), allowing for direct constraints on companion material. While most known events show evidence for dense nearby CSM identified via peak-light spectroscopy (as SNe Ia-CSM), targeted late-time searches have revealed a handful of cases exhibiting delayed CSM interaction with detached shells. Here, we present the first all-sky search for late CSM interaction in SNe Ia using a new image-subtraction pipeline for mid-infrared data from the NEOWISE space telescope. Analyzing a sample of $\approx8500$ SNe Ia, we report evidence for late-time mid-infrared brightening in five previously overlooked events spanning sub-types SNe Iax, SNe Ia-91T and super-Chandra SNe Ia. Our systematic search doubles the known sample, and suggests that $\gtrsim 0.05$\% of SNe Ia exhibit mid-infrared signatures of delayed CSM interaction. The mid-infrared light curves ubiquitously indicate the presence of multiple (or extended) detached CSM shells located at $\gtrsim 10^{16}-10^{17}$ cm, containing $10^{-6}-10^{-4}$~$M_\odot$ of dust, with some sources showing evidence for new dust formation, possibly within the cold, dense shell of the ejecta. We do not detect interaction signatures in spectroscopic and radio follow-up; however, the limits are largely consistent with previously confirmed events given the sensitivity and observation phase. Our results highlight that CSM interaction is more prevalent than previously estimated from optical and ultraviolet searches, and that mid-infrared synoptic surveys provide a unique window into this phenomenon.