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Recent improvements to the Cepheid distance scale

Published online by Cambridge University Press:  15 February 2018

Wendy L. Freedman
Affiliation:
Carnegie Observatories, 813 Santa Barbara Street, Pasadena, California 91101
Barry F. Madore
Affiliation:
NASA/IPAC Extragalactic Database, IPAC/JPL/Caltech MC 100-22, Pasadena, California 91125

Abstract

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In the course of the last decade significant advances have been made in the observations of Cepheid variables and in their successful application to the extragalactic distance scale. Much of this progress has come about as a result of new CCD and near-infrared photometry. These recent improvements are discussed, and a comparison is given of Population I Cepheids and Population II distances. The correspondence is good, with the zero points agreeing at a level of better than 15% in distance. At this same level of significance, a systematic difference between these distances scales may exist, in the sense that the RR Lyrae distances appear to be smaller than the Cepheid distances (if it is assumed, as has generally been done for extragalactic studies of RR Lyraes, that Mv(RR) = 0.77 mag, independent of [Fe/H]). However, several recently-published calibrations of Mv(RR) significantly reduce this discrepancy. Finally, new Cepheid data for the nearby galaxy M81 are presented based on recent Hubble Space Telescope observations.

Type
Variable Stars as Distance Indicators
Copyright
Copyright © Cambridge University Press 1993

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