Spitzer's Last Look at Extragalactic Explosions: Long-Term Evolution of\n Interacting Supernovae

Here we present new - and, nevertheless, last - mid-infrared (mid-IR) data\nfor supernovae (SNe) based on measurements with the Spitzer Space Telescope.\nComparing our recent 3.6 and 4.5 $\\mu$m photometry with previously published\nmid-IR and further multiwavelength datasets, we were able to draw some\nconclusions about the origin and heating mechanism of the dust in these SNe or\nin their environments, as well as on possible connection with circumstellar\nmatter (CSM) originating from pre-explosion mass-loss events in the progenitor\nstars. We also present new results regarding both certain SN classes and single\nobjects. We highlight the mid-IR homogeneity of SNe Ia-CSM, which may be a hint\nof their common progenitor type and of their basically uniform circumstellar\nenvironments. Regarding single objects, it is worth highlighting the late-time\ninteracting Type Ib SNe 2003gk and 2004dk, for which we present the first-ever\nmid-IR data, which seem to be consistent with clues of ongoing CSM interaction\ndetected in other wavelength ranges. Our current study suggests that long-term\nmid-IR follow-up observations play a key role in a better understanding of both\npre- and post-explosion processes in SNe and their environments. While Spitzer\nis not available any more, the expected unique data from the James Webb Space\nTelescope, as well as long-term near-IR follow-up observations of dusty SNe,\ncan bring us closer to the hidden details of this topic.\n