Photometry at 3.4 and 4.6 \micron of 128 Population I WC type Wolf-Rayet stars in the Galaxy and 12 in the Large Magellanic Cloud ( LMC ) observed in the WISE NEOWISE-R survey was searched for evidence of circumstellar dust emission and its variation .
Infrared spectral energy distributions ( SEDs ) were assembled , making use of archival r , i , Z and Y photometry to determine reddening and stellar wind levels for the WC stars found in recent IR surveys and lacking optical photometry .
From their SEDs , ten apparently non-variable stars were newly identified as dust makers , including three , WR 102-22 , WR 110-10 and WR 124-10 , having subtype earlier than WC8–9 , the first such stars to show this phenomenon .
The 11 stars found to show variable dust emission include six new episodic dust-makers , WR 47c , WR 75-11 , WR 91-1 , WR 122-14 and WR 125-1 in the Galaxy and HD 38030 in the LMC .
Of previously known dust makers , NEOWISE-R photometry of WR 19 captured its rise to maximum in 2018 confirming the 10.1-y period , that of WR 125 the beginning of a new episode of dust formation suggesting a period near 28.3 y. while that of HD 36402 covered almost a whole period and forced revision of it to 5.1 y .