Rescued from oblivion: detailed analysis of archival <i>Spitzer</i> data of SN 1993J

ABSTRACT We present an extensive analysis of the late-time mid-infrared (mid-IR) evolution Type IIb SN 1993J from 10–26 yr post-explosion based on archival – mostly previously unpublished photometric data Spitzer Space Telescope in conjunction with InfraRed Spectrograph spectrum. is one best-studied supernovae (SNe) decade-long multiwavelength set published various papers; however, its detailed mid-IR still missing literature. Mid-IR follow not just continuously cooling ejecta but also dust-formation and circumstellar-interaction processes. provide evidence that observed excess can be described by presence two-component local dust a mass ?(3.5–6.0) × 10?3 M? case partly silicate-based composition. The source these components could either newly formed grains or heating pre-existing via ongoing circumstellar matter interaction detected at other wavelengths. If it formed, assumed to located both unshocked inner outer cold dense shell, as Cassiopeia A remnant dust-forming SNe few years after explosion.