On the dynamical evolution of Cepheids in star clusters
  We investigate the occurrence of classical (type-I) Cepheid variable stars
(henceforth: Cepheids) in dynamically evolving star clusters from birth to an
age of approximately 300 Myr. The clusters are modelled by the Aarseth code
nbody6, and they feature a realistic stellar initial mass function and initial
binary star population, single star and binary star evolution, expulsion of the
primordial gas, and the tidal field of the galaxy. Our simulations provide the
first detailed dynamical picture of how frequently Cepheids remain
gravitationally bound to their birth clusters versus how frequently they occur
in the field. They allow us to quantify the relevance of various cluster escape
mechanisms and how they depend on stellar mass. Overall, the simulations agree
with the empirical picture that a small fraction ($\approx 10\%$) of Cepheids
reside in clusters, that cluster halo membership is relatively common, and that
the majority of Cepheid hosting clusters have only a single Cepheid member.
Additionally, the simulations predict that a) Cepheid progenitors are much more
likely to escape from low-mass than higher-mass clusters; b) higher-mass
(long-period) Cepheids are $\approx 30\%$ more likely to be found in clusters
than low-mass (short-period) Cepheids; c) the clustered Cepheid fraction
increases with galactocentric radius since cluster dispersal is less efficient
at greater radii; d) a lower metallicity reduces the overall clustered Cepheid
fraction; e) high-mass clusters are much more likely to have more than one
Cepheid member at any given time, in particular at a lower metallicity. We
interpret the results as outcomes of various aspects of star cluster dynamics.
The comparison of predicted and observed clustered Cepheid fractions, $f_{\rm
CC}$, highlights the need for additional cluster disruption mechanisms, most
likely encounters with giant molecular clouds.
