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UBV Magnitudes and Colours of 62 RR Lyrae Stars in ω Centauri (NGC 5139)

Published online by Cambridge University Press:  12 April 2016

E. H. Geyer
E. H. Geyer*
Affiliation:
Astron. Institut der Universität Bonn, Observatorium Hoher List, Bonn, Germany

Extract

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It has been shown by the author (Geyer, 1967), and independently by Dickens and Woolley (1967), that there occur horizontal branch stars well within the RR Lyrae variable gap of the c–m-diagram of ω Centauri. Variability of these objects is not known, and presumably is unlikely, because the cluster is so well studied for variable stars. For the observationally best studied globular clusters M3, M13, M15 and M92 (Sandage, 1969), this phenomenon is not found. The author’s original published c–w-diagram of NGC 5139 showed about 10 stars with (B–V)≥0.2 and V-magnitudes comparable with those of RR Lyrae stars of the cluster. Unpublished photoelectric measurements of some of these stars, carried out in 1968 with the 40-in photometric reflector of ESO by the author, support this finding. Also the study of blue horizontal branch stars by Newell, Rodgers and Searle (1969) of the Herst-monceux catalog of ω Centauri (Woolley et al., 1966) confirms these results, the importance of which for the understanding of the horizontal branch stars and RR Lyrae variables is obvious.

Type
Part II / RR Lyrae Variables in Population II Systems
Information
International Astronomical Union Colloquium , Volume 21: Variable Stars in Globular Clusters and in Related Systems , August 1973 , pp. 88 - 94
Copyright
Copyright © Reidel 1973

References

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