Locating Red Supergiants in the Galaxy NGC 6822
  Using archival near-IR photometry, we identify 51 of the K-band brightest red
supergiants (RSGs) in NGC 6822 and compare their physical properties with
stellar evolutionary model predictions. We first use Gaia parallax and proper
motion values to filter out foreground Galactic red dwarfs before constructing
a J - K vs. K color-magnitude diagram to eliminate lower-mass asymptotic giant
branch star contaminants in NGC 6822. We then cross-match our results to
previously spectroscopically confirmed RSGs and other NGC 6822 content studies
and discuss our overall completeness, concluding that radial velocity alone is
an insufficient method of determining membership in NGC 6822. After
transforming the J and K magnitudes to effective temperatures and luminosities,
we compare these physical properties with predictions from both the Geneva
single-star and Binary Population and Spectral Synthesis (BPASS) single and
binary star evolution tracks. We find that our derived temperatures and
luminosities match the evolutionary model predictions well, however the BPASS
model that includes the effects of binary evolution provides the best overall
fit. This revealed the presence of a group of cool RSGs in NGC 6822, suggesting
a history of binary interaction. We hope this work will lead to further
comparative RSG studies in other Local Group galaxies, opportunities for direct
spectroscopic follow-up, and a better understanding of evolutionary model
predictions.
