Cepheids in Open Clusters: An 8-D All-sky Census
  Cepheids in open clusters (cluster Cepheids: CCs) are of great importance as
zero-point calibrators of the Galactic Cepheid period-luminosity relationship
(PLR). We perform an 8-dimensional all-sky census that aims to identify new
bona-fide CCs and provide a ranking of membership confidence for known CC
candidates according to membership probabilities. The probabilities are
computed for combinations of known Galactic open clusters and classical Cepheid
candidates, based on spatial, kinematic, and population-specific membership
constraints. Data employed in this analysis are taken largely from published
literature and supplemented by a year-round observing program on both
hemispheres dedicated to determining systemic radial velocities of Cepheids. In
total, we find 23 bona-fide CCs, 5 of which are candidates identified for the
first time, including an overtone-Cepheid member in NGC 129. We discuss a
subset of CC candidates in detail, some of which have been previously mentioned
in the literature. Our results indicate unlikely membership for 7 Cepheids that
have been previously discussed in terms of cluster membership. We furthermore
revisit the Galactic PLR using our bona fide CC sample and obtain a result
consistent with the recent calibration by Turner (2010). However, our
calibration remains limited mainly by cluster uncertainties and the small
number of long-period calibrators. In the near future, Gaia will enable our
study to be carried out in much greater detail and accuracy, thanks to data
homogeneity and greater levels of completeness.
