RR lyrae stars in the globular cluster NGC 6101

Abstract

V- and I-band observations were taken over 9 months to study the RR Lyrae population in the metal-poor diffuse globular cluster NGC6101. We identify one new variable, which is either a potential long-period red giant variable or eclipsing binary, and recover all previously identified RR Lyraes. One previously studied RR Lyrae is reclassified as an RRc type, while two period estimations have been significantly refined. We confirm that NGC6101 is Oosterhoff type II with a high ratio of n(c)/n(ab+c)=0.833 with a very long mean RRab period of 0.86d. By using theoretical RR Lyrae period-luminosity- metallicity relations, we use our V- and I-band RR Lyrae data to gain an independent estimate of the reddening towards this cluster of E(B-V)=0.15 ± 0.04 and derive a distance of 12.8 ± 0.8kpc. The majority of the work in this study was undertaken by upper secondary school students involved in the Space to Grow astronomy education project in Australia. © 2012 Astronomical Society of Australia.