Characterizing the Population of Bright Infrared Sources in the Small
  Magellanic Cloud
  We used Spitzer's Infrared Spectrograph (IRS) to observe stars in the Small
Magellanic Cloud (SMC) selected from the Midcourse Space Experiment (MSX) Point
Source Catalog. We concentrate on the dust properties of oxygen-rich evolved
stars, which show less alumina than Galactic stars. This difference may arise
from the SMC's lower metallicity, but it could be a selection effect: the SMC
sample includes more stars which are brighter and thus more massive. The
distribution of SMC stars along the silicate sequence looks more like that of
Galactic red supergiants than asymptotic giant branch stars (AGBs). While many
are definitively AGBs, several SMC stars show evidence of hot bottom burning.
Other sources show mixed chemistry (oxygen-rich and carbon-rich features),
including supergiants with PAH emission. MSX SMC 134 may be the first confirmed
silicate/carbon star in the SMC, and MSX SMC 049 is a post-AGB candidate. MSX
SMC 145, previously a candidate OH/IR star, is actually an AGB star with a
background galaxy at z=0.16 along the same line-of-sight. We consider the
overall characteristics of all the {\em MSX} sources, the most infrared-bright
objects in the SMC, in light of {\em Spitzer}'s higher sensitivity and
resolution, and compare them with the object types expected from the original
selection criteria. This population represents what will be seen in more
distant galaxies by the James Webb Space Telescope (JWST). Color-color diagrams
using the IRS spectra and JWST mid-infrared filters show how one can separate
evolved stars from young stellar objects (YSOs) and distinguish among different
YSO classes.
