Richard I. Anderson, Laurent Eyer, Nami Mowlavi
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 through membership probabilities. The probabilities are computed for combinations of known Galactic open clusters and classical Cepheid candidates, based on spatial, kine- matic, and population-specific membership constraints. Data employed in this analysis are taken largely from published literature and supplemented by a year-round observ- ing program on both hemispheres dedicated to determining systemic radial velocities of Cepheids. In total, we find 13 bona-fide CCs, 3 of which are identified for the first time, including an overtone-Cepheid member in NGC 129. Inconclusive cases are discussed in detail, some of which have been previously mentioned in the literature. Our results are inconsistent with membership for 7 candidates that have been studied previously. We employ our bona-fide CC sample to revisit the Galactic PLR and obtain results consistent with most other calibrations, being limited by cluster uncertainties. 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.
View original:
http://arxiv.org/abs/1212.5119
No comments:
Post a Comment