Kavli Affiliate: Nathan P. Lourie
| First 5 Authors: Geoffrey Mo, Kishalay De, Eli Wiston, Nayana A. J., Raffaella Margutti
| Summary:
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 $approx 8500$ SNe
Ia, we report evidence for late-time mid-infrared brightening in six previously
overlooked events spanning sub-types SNe Iax, normal SNe Ia, SNe Ia-91T and
super-Chandra SNe Ia. Our systematic search doubles the known sample, and
suggests that $gtrsim 0.1$% 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 $10^{-4}-10^{-2}$ $M_odot$ of dust, with some
sources showing evidence for new dust formation, likely 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.
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