Supernova 2014C: ongoing interaction with extended circumstellar
  material with silicate dust
  Supernova (SN) 2014C is a unique explosion where a seemingly typical
hydrogen-poor stripped envelope SN started to interact with a dense,
hydrogen-rich circumstellar medium (CSM) a few months after the explosion. The
delayed interaction suggests a detached CSM shell, unlike in a typical SN IIn
where the CSM is much closer and the interaction commences earlier
post-explosion; indicating a different mass loss history. We present near- to
mid-infrared observations of SN 2014C from 1-5 years after the explosion,
including uncommon 9.7 $\mu$m imaging with COMICS on the Subaru telescope.
Spectroscopy shows that the interaction is still ongoing, with the
intermediate-width He I 1.083 $\mu$m emission present out to our latest epoch
1639 days post-explosion. The last Spitzer/IRAC photometry at 1920 days
post-explosion further confirms ongoing CSM interaction. The 1-10 $\mu$m
spectral energy distributions (SEDs) can be explained by a dust model with a
mixture of 69% carbonaceous and 31% silicate dust, pointing to a chemically
inhomogeneous CSM. The inference of silicate dust is the first among
interacting SNe. An SED model with purely carbonaceous CSM dust is possible,
but would require more than 0.22 $M_{\odot}$ of dust, which is an order of
magnitude larger than what observed in any other SNe, measured in the same way,
at this epoch. The light curve beyond 500 days is well fit by an interaction
model with a wind-driven CSM and a mass loss rate of $\sim 10^{-3} \,
M_{\odot}\,\rm yr^{-1}$, which presents an additional CSM density component
exterior to the constant density shell reported previously in the literature.
SN 2014C could originate in a binary system, similar to RY Scuti, which would
explain the observed chemical and density profile inhomogeneity in the CSM.
