The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity
2017
We present the results of our survey of 1612 MHz circumstellar OH maser emission
from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large
Magellanic Cloud. We have discovered four new circumstellar maser sources in the
LMC, and increased the number of reliable wind speeds from IR stars in the LMC
from 5 to 13. Using our new wind speeds, as well as those from Galactic sources,
we have derived an updated relation for dust driven winds: vexp / ZL0:4. We compare
the sub-solar metallicity LMC OH/IR stars with carefully selected samples of
more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and
Galactic Bulge. For 8 of the Bulge stars we derive pulsation periods for the first
time, using near-IR photometry from the VVV survey. We have modeled our LMC
OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and
mass loss rates by scaling the models to the results from maser profiles. We have
done this also for samples in the Galactic Centre and Bulge and derived a new
mass loss prescription that includes luminosity, pulsation period, and gas-to-dust ratio
_M
= 1:06+3:5
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