Volume 494, Number 2, February I 2009
|Page(s)||L17 - L20|
|Published online||14 January 2009|
Letter to the Editor
Double mode RR Lyrae stars in Omega Centauri
Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warszawa, Poland e-mail: [olech;pam]@camk.edu.pl
Accepted: 23 December 2008
Aims. The aim of this work is to search for double mode pulsators among RR Lyr variables of globular cluster ω Cen.
Methods. We conducted a systematic frequency analysis of CASE photometry of ω Cen RR Lyr stars. We searched for periodicities using Fourier and ANOVA periodograms, combined with a consecutive prewhitening technique.
Results. We discovered six double mode pulsators, with the first overtone and a secondary mode of higher frequency simultaneously excited. These are the first double mode RR Lyr stars identified in ω Cen. In variable V10 the period ratio of the two modes is 0.80, which corresponds to pulsations in the first and second radial overtones. In V19 and V105 we found an unexpected period ratio of 0.61. Three other stars display period ratios of either ~ 0.80 or ~ 0.61, depending on the choice of aliases.
Conclusions. While the period ratio of ~0.80 is easy to interpret in terms of the two lowest radial overtones, the value of ~0.61 cannot be explained by any two radial modes. Thus, V19 and V105 are the first members of a new class of double mode RR Lyr pulsators.
Key words: stars: oscillations / stars: horizontal-branch / Galaxy: globular clusters: individual: ω Centauri
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.