NGC 129 and the Cepheid DL Cas

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Session 6 -- Cepheid Variables and the Distance Scale
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

[6.03] NGC 129 and the Cepheid DL Cas

A.M. Fry and B.W. Carney (Univ. North Carolina)

The zeropoint of the Cepheid extragalactic distance scale is set by main sequence fitting to the Pleiades. In order to optimize the fitting, it is necessary to know the difference in metallicity between the cluster being fitted and the Pleiades; a 0.1 dex difference in metallicity can lead to a 0.1 dex error in derived distance. We have obtained high- resolution echelle spectra of 15 of the Cepheids used to calibrate the period-luminosity relation and are finding a 0.5 dex spread in metallicity. We have also obtained UBV photometry of NGC 129, NGC 6087, and NGC 5662 in order to go deeper down the main sequences of these clusters and have obtained JK photometry of NGC 129 and NGC 6087 in order to exploit the advantages of the flatter main sequences in K vs V-K.

We present a new color-magnitude diagram for NGC 129 and an abundance analysis of DL Cas.

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