Monitoring Cepheid Period Changes from Saint Mary's University

Volume 27 number 1 (1999)

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David G. Turner

Andrew J. Horsford

Andrew J. Horsfold

Joseph MacMillan

Abstract

CCD observations in blue light with the 0.4m telescope at Saint Mary's University are presented for the Cepheids SU Cyg, V402 Cyg, V1154 Cyg, V386 Cyg, V924 Cyg, MW Cyg, BB Her, GH Cyg, VY Cyg, TX Cyg, SZ Cyg, X Cyg, CD Cyg, and CV Vul. The data are used to establish new times of light maximum for the sample, and analyses of the new and previously-published O-C residuals are used to derive improved values for the rates of period change for each program object. The new values agree closely with predictions from stellar evolutionary theory for the rates at which intermediate-mass stars evolve through the Cepheid instability strip, and provide an excellent means of establishing the instability strip crossing mode for each variable.