JWST/MIRI detects the dusty SN1993J about 30 years after explosion

Abstract

Core-collapse supernovae (CCSNe) have long been considered to contribute significantly to the cosmic dust budget. New dust cools quickly and is therefore detectable at mid-infrared (mid-IR) wavelengths. However, before the era of the James Webb Space Telescope (JWST), direct observational evidence for dust condensation was found in only a handful of nearby CCSNe, and dust masses (~10$^{-2}-10^{-3} M_{\odot}$, generally limited to <5 yr and to >500K temperatures) have been 2-3 orders of magnitude smaller than either theoretical predictions or dust amounts found by far-IR/submm observations of Galactic SN remnants and in the very nearby SN 1987A. The combined angular resolution and mid-IR sensitivity of JWST finally allow us to reveal hidden cool (~100-200K) dust reservoirs in extragalactic SNe beyond SN 1987A. Our team received JWST/MIRI time for studying a larger sample of CCSNe to fill the currently existing gap in their dust formation histories. The first observed target of this program is the well-known Type IIb SN~1993J appeared in M81. We generated its spectral energy distribution (SED) from the current JWST/MIRI F770W, F1000W, F1500W, and F2100W fluxes. We fit single- and two-component silicate and carbonaceous dust models to the SED. We found that SN 1993J still contains a significant amount (~0.01 $M_{\odot}$) of dust ~30 yr after explosion. Comparing these results to those of the analysis of earlier {Spitzer Space Telescope data, we see a similar amount of dust now that was detected ~15-20 yr ago, but at a lower temperature. We also find residual background emission near the SN site (after point-spread-function subtraction on the JWST/MIRI images) that may plausibly be attributed to an IR echo from more distant interstellar dust grains heated by the SN shock-breakout luminosity or ongoing star formation in the local environment.