Variable Stars in Globular Clusters and in Related Systems : Proceedings of the IAU Colloquium No. 21 Held at the University of Toronto, Toronto, Canada August 29–31, 1972

This volume contains the papers and discussions at IAU Colloquium No. 21 on Variable Stars in Globular Clusters and in Related Systems held in Toronto on the 29th, 30th and 31st August 1972. It was the intention of the organizers that this meeting should honour the life long work in this field of Professor Helen Sawyer Hogg. She has been continuously active in observational research on variables in globular clusters for 46 years and her catalogues and bibliographies as well as her research papers, review articles and IA U reports as chairman of the committee on variable stars in clusters are of fundamental importance to all workers in this field. The scope of the colloquium covered both observational and theoretical aspects of the problem, including the relationship of variables to non-variable cluster members, the position of the variables in the HR diagram and their importance for problems of stellar evolution, empirical data on the variables, periods and period changes, and the relevant parts of pulsation theory. The meeting was particularly successful in bringing together observers and theorists. It will have achieved its object if it has shown both observers and theorists which are the problems most suitable for attack at the present time. The meeting clearly demonstrated the great importance of research on variables in globular clusters and related systems for our understanding both of stellar evolution and stellar pulsation. Front Matter....Pages I-IX Front Matter....Pages 1-1 Variables in Globular Clusters, the Common and the Rare....Pages 3-7 Some Problems in the Study of Variable Stars in Globular Clusters....Pages 8-20 Observations of Faint Globular Clusters....Pages 21-25 Planetary Nebulae, Globular Clusters and the Galactic Halo....Pages 26-28 An Abundance Analysis of Fehrenbach’s Star (HD 116745) in Omega Centauri....Pages 29-30 On the Nature of the 41-Day Cycle of RR Lyrae....Pages 31-34 Variable Stars in Dwarf Spheroidal Galaxies....Pages 35-48 Front Matter....Pages 49-49 Observational Aspects of RR Lyrae Variables in Globular Clusters....Pages 51-67 New Variable Stars in the Globular Cluster NGC 6401....Pages 68-75 Variable Stars in NGC 4590....Pages 76-81 Two-Colour Photometry of RR Lyrae Variables in NGC 6981....Pages 82-83 Intermediate Band Photometry of RR Lyrae Variables in ω Cen and 47 Tuc....Pages 84-87 UBV Magnitudes and Colours of 62 RR Lyrae Stars in ω Centauri (NGC 5139)....Pages 88-94 Two-Color Observations of RR Lyrae Stars in M14....Pages 95-100 On the Changes of Periods of RR Lyrae Variables in the Globular Clusters M5, M53 and NGC 5053....Pages 101-103 Period and Period Changes of RR Lyrae Variables in M15....Pages 104-104 Period Changes as Evidence for Evolution in ω Cen....Pages 105-112 Short Period Variables in the Magellanic Cloud Cluster NGC 1466....Pages 113-119 The RR Lyrae Stars in the Magellanic Clouds....Pages 120-128 Front Matter....Pages 129-129 Observational Aspects of Slow Variables in Globular Clusters....Pages 131-144 Front Matter....Pages 129-129 A Preliminary Investigation of Period Changes for W Virginis Stars in Globular Clusters....Pages 145-149 Mean Magnitudes and Colours of Six Cepheids in Three Red Globular Clusters of the Large Magellanic Cloud....Pages 150-150 Red Variable Stars in Metal Rich Globular Clusters....Pages 151-163 Narrow-Band Photometry of Red Variables in Globular Clusters....Pages 164-177 The Variable Stars in NGC 6723....Pages 178-179 The Period-Luminosity Relation for Cepheids in Globular Clusters....Pages 180-184 Front Matter....Pages 185-185 Variable Stars and Evolution in Globular Clusters....Pages 187-195 On the Two Oosterhoff Groups of Globular Clusters....Pages 196-196 On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems....Pages 197-206 Possible Evolutionary Interpretation of the Dependences on the Diagrams for RR Lyrae Variables....Pages 207-213 The Evolutionary Status of Population II Cepheids....Pages 214-220 Semiconvection and the RR Lyrae Variables....Pages 221-228 The Helium Abundance in the Envelopes of the Bluest RR Lyrae Stars in Globular Clusters and Dependence of Globular Cluster Variable Star Properties on Chemical Composition....Pages 229-234 Back Matter....Pages 235-236 Proceedings of the IAU Colloquium No. 21 held at the University of Toronto, Toronto, Canada, August 29-31, 1972