Variable Stars with Periods Greater than One Day in Globular Clusters

Author: Arp, Halton Christian

Year: 1953

Degree: Dissertation (Ph.D.)

Advisor: Baade, Walter

Committee Member: Unknown, Unknown

Option: Astronomy; Physics

DOI: 10.7907/SMXJ-NH60

Abstract

Nineteen variable stars with periods greater than one day were observed in six globular clusters. The observational techniques and the accuracy of the measurements are discussed and light curves for 15 variables are exhibited.

Color-magnitude diagrams for six clusters are presented and the distance modulus to each is derived.

The resulting period-luminosity relation for type II cepheids indicates there are actually three separate lines in the period-luminosity diagram which these variables occupy. Means of identifying stars on these different lines are presented. The factor of two in the period which these lines are from each other is discussed from the standpoint of the nature of cepheid variation. Finally a hypothesis is advanced to explain the connection between type I and type II cepheids.

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