NEOWISE-R Caught the Luminous SN 2023ixf in Messier 101

TL;DR

This paper reports on the early and late-time mid-infrared observations of supernova SN 2023ixf in Messier 101 by NEOWISE-R, revealing dust formation, shock interaction, and unique IR excess features in unprecedented detail.

Contribution

First detailed mid-infrared observational analysis of SN 2023ixf, highlighting dust heating, shock interaction, and IR excess phenomena in a luminous Type II supernova.

Findings

Early IR excess from dust heated by CSM interaction

Late-time IR excess possibly from newly formed dust or CO emission

SN 2023ixf is among the most luminous SNe IIP observed in mid-IR

Abstract

The reactivated Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE-R) serendipitously caught the Type II supernova SN 2023ixf in Messier 101 on the rise, starting day 3.6 through day 10.9, and on the late-time decline from days 211 through 213 and days 370 through 372. We have considered these mid-infrared (mid-IR) data together with observations from the ultraviolet (UV) through the near-IR, when possible. At day 3.6 we approximated the optical emission with a hot, ~26,630 K blackbody, with a notable UV excess likely from strong SN shock interaction with circumstellar matter (CSM). In the IR, however, a clear excess is also obvious, and we fit it with a cooler, ~1,620 K blackbody with radius of ~2.6 x 10^{15} cm, consistent with dust in the progenitor's circumstellar shell likely heated by the UV emission from the CSM interaction. On day 10.8, the light detected was consistent with SN ejecta-dominated emission. At late times we also observed a clear NEOWISE-R excess, which could arise either from newly formed dust in the inner ejecta or in the contact discontinuity between the forward and reverse shocks, or from more distant pre-existing dust grains in the SN environment. Furthermore, the large 4.6 micron excess at late times can also be explained by the emergence of the carbon monoxide 1--0 vibrational band. SN 2023ixf is the best-observed SN IIP in the mid-IR during the first several days after explosion and one of the most luminous such SNe ever seen.