The overlooked role of stellar variability in the extended main sequence
  of LMC intermediate-age clusters
  Intermediate-age star clusters in the Large Magellanic Cloud show extended
main sequence turn offs (MSTOs), which are not consistent with a canonical
single stellar population. These broad turn offs have been interpreted as
evidence for extended star formation and/or stellar rotation. Since most of
these studies use single frames per filter to do the photometry, the presence
of variable stars near the MSTO in these clusters has remained unnoticed and
their impact totally ignored. We model the influence of Delta Scuti using
synthetic CMDs, adding variable stars following different levels of incidence
and amplitude distributions. We show that Delta Scuti observed at a single
phase will produce a broadening of the MSTO without affecting other areas of a
CMD like the upper MS or the red clump; furthermore, the amount of spread
introduced correlates with cluster age as observed. This broadening is
constrained to ages ~ 1-3 Gyr when the MSTO area crosses the instability strip,
which is also consistent with observations. Variable stars cannot explain
bifurcated MSTOs or the extended MSTOs seen in some young clusters, but they
can make an important contribution to the extended MSTOs in intermediate-age
clusters.
