DUSTiNGS II. Metal-poor dusty AGB stars

Using two epochs, spaced approximately six months apart, we identify a total of 526 dusty variable AGB stars (sometimes called "extreme" or x-AGB stars; [3.6]-[4.5]>0.1mag). Of these, 111 are in galaxies with [Fe/H]<-1.5 and 12 are in galaxies with [Fe/H]<-2.0, making them the most metal-poor dust-producing AGB stars known.

We compare these identifications to those in the literature and find that most are newly discovered large-amplitude variables, with the exception of {approx}30 stars in NGC185 and NGC147, 1 star in IC1613, and 1 star in Phoenix. The chemical abundances of the x-AGB variables are unknown, but the low metallicities suggest that they are more likely to be carbon-rich than oxygen-rich and comparisons with existing optical and near-IR photometry confirm that 70 of the x-AGB variables are confirmed or likely carbon stars.