Christine M. Clement et al. 2001 The Astronomical Journal 122 2587 doi:10.1086/323719
Christine M. Clement1, Adam Muzzin1, Quentin Dufton1, Thivya Ponnampalam1, John Wang1, Jay Burford1, Alan Richardson1, Tara Rosebery1, Jason Rowe2 and Helen Sawyer Hogg3
Show affiliationsBased on a search of the literature up to 2001 May, the number of known variable stars in Galactic globular clusters is approximately 3000. Of these, more than 2200 have known periods and the majority (approximately 1800) are of the RR Lyrae type. In addition to the RR Lyrae population, there are approximately 100 eclipsing binaries, 120 SX Phoenicis variables, 60 Cepheids (including Population II Cepheids, anomalous Cepheids and RV Tauri), and 120 SR/red variables. The mean period of the fundamental mode RR Lyrae variables is 0.585 days, for the overtone variables it is 0.342 days (0.349 days for the first-overtone pulsators and 0.296 days for the second-overtone pulsators) and approximately 30% are overtone pulsators. These numbers indicate that about 65% of RR Lyrae variables in Galactic globular clusters belong to Oosterhoff type I systems. The mean period of the RR Lyrae variables in the Oosterhoff type I clusters seems to be correlated with metal abundance in the sense that the periods are longer in the more metal poor clusters. Such a correlation does not exist for the Oosterhoff type II clusters. Most of the Cepheids are in clusters with blue horizontal branches.
binaries: eclipsing; Cepheids; globular clusters: general; stars: horizontal-branch; stars: oscillations
Issue 5 (2001 November)
Received 2001 July 18, accepted for publication 2001 July 30
Christine M. Clement et al. 2001 The Astronomical Journal 122 2587
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