Does Collinder 236 host a Cepheid calibrator?

Abstract

Photoelectric UBV photometry and star counts are presented for the previously unstudied open cluster Collinder 236, supplemented by observations for stars near the Cepheid WZ Car. Collinder 236 is typical of groups associated with Cepheids, with an evolutionary age of (3.4+-1.1)x10^7 years, but it is 1944+-71 pc distant, only half the predicted distance to WZ Car. The cluster is reddened by E(B-V)~0.26, and has nuclear and coronal radii of rn~2 arcmin (1.1 pc) and Rc~8 arcmin (4.5 pc), respectively. The Cepheid is not a member of Collinder 236 on the basis of location beyond the cluster tidal radius and implied distance, but its space reddening can be established as E(B-V)=0.268+-0.006 s.e. from 5 adjacent stars. Period changes in WZ Car studied with the aid of archival data are revised. The period of WZ Car is increasing, its rate of +8.27+-0.19 s yr^(-1) being consistent with a third crossing of the instability strip.

arXiv commentAccepted for publication (MNRAS)

References in corpus (9)

• Hubble Space Telescope Fine Guidance Sensor Parallaxes of Galactic Cepheid Variable Stars: Period-Luminosity Relations
• A new calibration of Galactic Cepheid Period-Luminosity relations from B to K bands, and a comparison to LMC PL relations
• Cepheid Parallaxes and the Hubble Constant
• Rate of Period Change as a Diagnostic of Cepheid Properties
• The Distances to Open Clusters from Main-Sequence Fitting. IV. Galactic Cepheids, the LMC, and the Local Distance Scale
• Fundamental parameters of Cepheids. V. Additional photometry and radial velocity for southern Cepheids
• Distances to Cepheid Open Clusters Via Optical and K-Band Imaging
• Assessing potential cluster Cepheids from a new distance and reddening parameterization and 2MASS photometry
• Galactic clusters with associated Cepheid variables. VII. Berkeley 58 and CG Cassiopeiae

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