The lifecycle of dust in the interstellar medium ( ISM ) is heavily influenced by outflows from asymptotic giant branch ( AGB ) and red supergiant ( RSG ) stars , a large fraction of which is contributed by a few very dusty sources .
We compute the dust input to the Small Magellanic Cloud ( SMC ) by fitting the multi-epoch mid-infrared spectral energy distributions ( SEDs ) of AGB/RSG candidates with models from the G rid of R SG and A GB M odel S ( GRAMS ) grid , allowing us to estimate the luminosities and dust-production rates ( DPRs ) of the entire population .
By removing contaminants , we guarantee a high-quality dataset with reliable DPRs and a complete inventory of the dustiest sources .
We find a global AGB/RSG dust-injection rate of ( 1.3 \pm 0.1 ) \times 10 ^ { -6 } M _ { \odot } yr ^ { -1 } , in agreement with estimates derived from mid-infrared colours and excess fluxes .
As in the LMC , a majority ( 66 % ) of the dust arises from the extreme AGB stars , which comprise only \approx 7 % of our sample .
A handful of far-infrared sources , whose 24 \mu m fluxes exceed their 8 \mu m fluxes , dominate the dust input .
Their inclusion boosts the global DPR by \approx 1.5 \times , making it necessary to determine whether they are AGB stars .
Model assumptions , rather than missing data , are the major sources of uncertainty ; depending on the choice of dust shell expansion speed and dust optical constants , the global DPR can be up to \approx 10 times higher .
Our results suggest a non-stellar origin for the SMC dust , barring as yet undiscovered evolved stars with very high DPRs .