The Multi-periodic Blazhko Modulation of CZ Lacertae

Abstract

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 ($\approx$14.6 d and $\approx$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, meanwhile, the mean pulsation amplitude slightly decreased. The modulation frequencies were in a 5:4 resonance ratio in the first observing season 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 $\approx$40-d modulation of RR Lyr. The mean values of the global physical parameters and their changes with Blazhko phase of both modulation components were determined by the Inverse Photometric Method.

12 pages, accepted for publication in MNRAS

References in corpus (10)

• Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
• Multiperiodic Galactic field RR Lyrae stars in the ASAS catalog
• An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: I. Light curve solution
• An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parameters
• CoRoT light curves of RR Lyrae stars. CoRoT 101128793: long-term changes in the Blazhko effect and excitation of additional modes
• First quintuplet frequency solution of a Blazhko variable: light curve analysis of RV UMa
• The Blazhko behaviour of RR Geminorum II -- long-term photometric results
• A new method for determining physical parameters of fundamental mode RR Lyrae stars from multicolour light curves
• The Unique Frequency Spectrum of the Blazhko RRc Star LS Her
• Studying Blazhko RR Lyrae stars with the 24-inch telescope of the Konkoly Observatory

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