Kathryn F. Neugent, Philip Massey, Brian Skiff, Georges Meynet
Due to their transitionary nature, yellow supergiants provide a critical
challenge for evolutionary modeling. Previous studies within M31 and the SMC
show that the Geneva evolutionary models do a poor job at predicting the
lifetimes of these short-lived stars. Here we extend this study to the LMC
while also investigating the galaxy's red supergiant content. This task is
complicated by contamination by Galactic foreground stars that color and
magnitude criteria alone cannot weed out. Therefore, we use proper motions and
the LMC's large systemic radial velocity (\sim278 km/s) to separate out these
foreground dwarfs. After observing nearly 2,000 stars, we identified 317
probable yellow supergiants, 6 possible yellow supergiants and 505 probable red
supergiants. Foreground contamination of our yellow supergiant sample was
\sim80%, while that of the the red supergiant sample was only 3%. By placing
the yellow supergiants on the H-R diagram and comparing them against the
evolutionary tracks, we find that new Geneva evolutionary models do an
exemplary job at predicting both the locations and the lifetimes of these
transitory objects.
View original:
http://arxiv.org/abs/1202.4225
No comments:
Post a Comment