We present high spatial resolution mid-infrared images of the nebula around the late-type carbon-rich Wolf-Rayet ( WC ) -OB binary system WR 112 taken by the recently upgraded VLT spectrometer and imager for the mid-infrared ( VISIR ) with the PAH1 , NeII_2 , and Q3 filters .
The observations reveal a morphology resembling a series of arc-like filaments and broken shells .
Dust temperatures and masses are derived for each of the identified filamentary structures , which exhibit temperatures ranging from 179 _ { -6 } ^ { +8 } K at the exterior W2 filament to 355 _ { -25 } ^ { +37 } K in the central 3 ” .
The total dust mass summed over the features is 2.6 \pm 0.4 \times 10 ^ { -5 } \mathrm { M } _ { \odot } .
A multi-epoch analysis of mid-IR photometry of WR 112 over the past \sim 20 yr reveals no significant variability in the observed dust temperature and mass .
The morphology of the mid-IR dust emission from WR 112 also exhibits no significant expansion from imaging data taken in 2001 , 2007 , and 2016 , which disputes the current interpretation of the nebula as a high expansion velocity ( \sim 1200 km s ^ { -1 } ) “ pinwheel ” -shaped outflow driven by the central WC-OB colliding-wind binary .
An upper limit of \lesssim 120 km s ^ { -1 } is derived for the expansion velocity assuming a distance of 4.15 kpc .
The upper limit on the average total mass-loss rate from the central 3 ” of WR 112 is estimated to be \lesssim 8 \times 10 ^ { -6 } \mathrm { M } _ { \odot } yr ^ { -1 } .
We leave its true nature as an open question , but propose that the WR 112 nebula may have formed in the outflow during a previous red or yellow supergiant phase of the central Wolf-Rayet star .