  WR 112 is a dust-forming carbon-rich Wolf-Rayet (WC) binary with a dusty
circumstellar nebula that exhibits a complex asymmetric morphology, which
traces the orbital motion and dust formation in the colliding winds of the
central binary. Unraveling the complicated circumstellar dust emission around
WR 112 therefore provides an opportunity to understand the dust formation
process in colliding-wind WC binaries. In this work, we present a multi-epoch
analysis of the circumstellar dust around WR 112 using seven high spatial
resolution (FWHM $\sim0.3-0.4''$) N-band ($\lambda \sim12$ $\mu$m) imaging
observations spanning almost 20 years and includes newly obtained images from
Subaru/COMICS in Oct 2019. In contrast to previous interpretations of a face-on
spiral morphology, we observe clear evidence of proper motion of the
circumstellar dust around WR 112 consistent with a nearly edge-on spiral with a
$\theta_s=55^\circ$ half-opening angle and a $\sim20$-yr period. The revised
near edge-on geometry of WR 112 reconciles previous observations of highly
variable non-thermal radio emission that was inconsistent with a face-on
geometry. We estimate a revised distance to WR 112 of $d =
3.39^{+0.89}_{-0.84}$ kpc based on the observed dust expansion rate and a
spectroscopically derived WC terminal wind velocity of $v_\infty= 1230\pm260$
km s$^{-1}$. With the newly derived WR 112 parameters we fit optically-thin
dust spectral energy distribution models and determine a dust production rate
of $\dot{M}_d=2.7^{+1.0}_{-1.3}\times10^{-6}$ M$_\odot$ yr$^{-1}$, which
demonstrates that WR 112 is one of the most prolific dust-making WC systems
known.

Solar and Stellar Astrophysics;Astrophysics of Galaxies