The properties of carbon stars in the Magellanic Clouds ( MCs ) and their total dust production rates are predicted by fitting their spectral energy distributions ( SED ) over pre-computed grids of spectra reprocessed by dust .
The grids are calculated as a function of the stellar parameters by consistently following the growth for several dust species in their circumstellar envelopes , coupled with a stationary wind .
Dust radiative transfer is computed taking as input the results of the dust growth calculations .
The optical constants for amorphous carbon are selected in order to reproduce different observations in the infrared and optical bands of Gaia Data Release 2 .
We find a tail of extreme mass-losing carbon stars in the Large Magellanic Cloud ( LMC ) with low gas-to-dust ratios that is not present in the Small Magellanic Cloud ( SMC ) .
Typical gas-to-dust ratios are around 700 for the extreme stars , but they can be down to \sim 160 – 200 and \sim 100 for a few sources in the SMC and in the LMC , respectively .
The total dust production rate for the carbon star population is \sim 1.77 \pm 0.45 \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } , for the LMC , and \sim 2.52 \pm 0.96 \times 10 ^ { -6 } M _ { \odot } yr ^ { -1 } , for the SMC .
The extreme carbon stars observed with the Atacama Large Millimeter Array and their wind speed are studied in detail .
For the most dust-obscured star in this sample the estimated mass-loss rate is \sim 6.3 \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } .
The grids of spectra are available at : https : //ambrananni085.wixsite.com/ambrananni/online-data-1 and included in the SED-fitting python package for fitting evolved stars https : //github.com/s-goldman/Dusty-Evolved-Star-Kit .