Journal Article

The multiperiodic Blazhko modulation of CZ Lacertae*

Á. Sódor, J. Jurcsik, B. Szeidl, M. Váradi, A. Henden, K. Vida, Zs. Hurta, K. Posztobányi, I. Dékány and A. Szing

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 3, pages 1585-1596
Published in print March 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI:
The multiperiodic Blazhko modulation of CZ Lacertae*

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A thorough analysis of the multicolour CCD observations of the RRab-type variable, CZ Lacertae, is presented. The observations were carried out in two consecutive observing seasons in 2004 and 2005 within the framework of the Konkoly Blazhko Survey of bright, northern, short-period RRab variables. The O − C variation of CZ Lac indicated that a significant period decrease took place just around the time of the CCD observations. Our data gave a unique opportunity to study the related changes in the pulsation and modulation properties of a Blazhko star in detail. Two different period components (≈ 14.6 and ≈ 18.6 d) of the Blazhko modulation were identified. Both modulation components had similar strength. The periods and amplitudes of the modulations changed significantly from the first season to the next, while the mean pulsation amplitude decreased slightly. The modulation frequencies were in a 5:4 resonance ratio in the first observing season, and then the frequencies shifted in opposite directions, and their ratio was close to the 4:3 resonance in the next season. The interaction of the two modulations caused beating with a period of 74 d in the first season, which resembled the 4-yr-long cycle of the ≈ 40-d modulation of RR Lyr. The mean values of the global physical parameters and their changes with the Blazhko phase of both modulation components were determined by the inverse photometric method.

Keywords: methods: data analysis; techniques: photometric; stars: horizontal branch; stars: individual: CZ Lac; stars: oscillations; stars: variables: RR Lyrae

Journal Article.  7599 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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