We present SOFIA/FORCAST imaging of the circumstellar dust shells surrounding the luminous blue variable ( LBV ) candidates MN 90 and HD 168625 to quantify the mineral abundances of the dust and to constrain the evolutionary state of these objects .
Our image at 37.1 \micron of MN 90 shows a limb-brightened , spherical dust shell .
A least-squares fit to the spectral energy distribution of MN 90 yields a dust temperature of 59 \pm 10 K , with the peak of the emission at 42.7 \micron .
Using 2-D ust radiative transfer code , we estimate for MN 90 that mass-loss occurred at a rate of ( 7.3 \pm 0.4 ) \times 10 ^ { -7 } M _ { \sun } yr ^ { -1 } \ > \times ( v _ { exp } / 50 { km s ^ { -1 } } ~ { } ) to create a dust shell with a dust mass of ( 3.2 \pm 0.1 ) \times 10 ^ { -2 } M _ { \sun } \ > .
Our images between 7.7 – 37.1 \micron of HD 168625 complement previously obtained mid-IR imaging of its bipolar nebulae .
The SOFIA/FORCAST imaging of HD 168625 shows evidence for the limb-brightened peaks of an equatorial torus .
We estimate a dust temperature of 170 \pm 40 K for the equatorial dust surrounding HD 168625 , with the peak of the emission at 18.3 \micron .
Our 2-D ust model for HD 168625 estimates that mass-loss occurred at a rate of ( 3.2 \pm 0.2 ) \times 10 ^ { -7 } M _ { \sun } yr ^ { -1 } \ > to create a dust torus/shell with a dust mass of ( 2.5 \pm 0.1 ) \times 10 ^ { -3 } M _ { \sun } \ > .