New MMT/MIRAC ( 9–11 \micron ) , SOFIA /FORCAST ( 11–37 \micron ) , and Herschel/PACS ( 70 and 160 \micron ) infrared ( IR ) imaging is presented for three famous OH/IR red supergiants ( NML Cyg , VX Sgr , and S Per ) and two normal red supergiants ( RS Per and T Per ) .
We model the observed spectral energy distributions ( SEDs ) using radiative transfer code DUSTY and the GRAMS grid of models .
Azimuthal average profiles from the SOFIA /FORCAST imaging , in combination with dust mass distribution profiles from DUSTY , constrain the mass-loss histories of these supergiants .
For VX Sgr , we resolve excess circumstellar emission above the point spread function ( PSF ) at 20–40 \micron , and we measure a constant mass-loss rate of 2 \times 10 ^ { -5 } \mathrm { M } _ { \odot } /yr .
SED modeling and resolved circumstellar emission with FORCAST and MIRAC suggest that S Per may have had a higher mass-loss rate in the past , with an average of \sim 1 - 3 \times 10 ^ { -5 } \mathrm { M } _ { \odot } /yr .
The radial profiles of RS Per and T Per are both best modeled with steep density gradients , \rho \left ( r \right ) \propto r ^ { -2.6 } and r ^ { -2.2 } dust mass distribution functions , which imply increased mass loss in the recent past .
Over the lifetimes of the observed dust shells , we estimate average mass-loss rates of 4 - 8 \times 10 ^ { -6 } \mathrm { M } _ { \odot } / yr for RS Per and 2 - 6 \times 10 ^ { -7 } \mathrm { M } _ { \odot } / yr for T Per .
Finally , although NML Cyg has resolved nebular emission in HST visual images and in the near-IR MIRAC images , we do not observe any circumstellar envelope at 20–40 \micron at FORCAST ’ s spatial resolution .
DUSTY modeling of NML Cyg suggests that its mass loss has been constant with time , with average mass-loss rates between 2 \times 10 ^ { -5 } and 4 \times 10 ^ { -4 } \mathrm { M } _ { \odot } / yr , estimated with the two modeling codes .
Combining our results with ( ) ( Paper I ) we find mixed results with some red supergiants showing evidence for variable and high mass-loss events while others have a constant mass loss over the past few thousand years .