The complex case of V445 Lyr observed with Kepler: two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more
Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as have recently been detected in high-precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme case detected so far, the RRab star V445 Lyr (KIC 6186029) which was observed with the Kepler space mission. V445 Lyr shows very strong cycle-to-cycle changes in its Blazhko modulation, which are caused by both a secondary long-term modulation period and irregular variations. In addition to the complex Blazhko modulation, V445 Lyr also shows a rich spectrum of additional peaks in the frequency range between the fundamental pulsation and the first harmonic. Among those peaks, the second radial overtone could be identified, which, combined with a metallicity estimate of [Fe/H] =−2.0 dex from spectroscopy, allowed us to constrain the mass (0.55–0.65 M_⊙) and luminosity (40–50 L_⊙) of V445 Lyr through theoretical Petersen diagrams. A non-radial mode and possibly the first overtone are also excited. Furthermore, V445 Lyr shows signs of the period-doubling phenomenon and a long-term period change. A detailed Fourier analysis along with a study of the O − C variation of V445 Lyr is presented, and the origin of the additional peaks and possible causes of the changes in the Blazhko modulation are discussed. The results are then put into context with those of the only other star with a variable Blazhko effect for which a long enough set of high-precision continuous satellite data has been published so far, the CoRoT star 105288363.
Additional Information© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 May 4; Received 2012 April 30; in original form 2012 February 23. Funding for this discovery mission is provided by NASA's Science Mission Directorate. EG acknowledges support from the Austrian Science Fund (FWF), project number P19962-N16. KK is presently a Marie Curie Fellow (IOF-255267). The research leading to these results has received funding from the European Commission's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 269194 (IRSES/ASK). RSz and JMB are supported by the Lendület programme of the Hungarian Academy of Sciences and the Hungarian OTKA grants K83790 and MB08C 81013. RSz was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences. C-CN thanks the funding from the National Science Council (of Taiwan) under the contract NSC 98-2112-M-008-013-MY3. We acknowledge the assistance of the queue observers, Chi-Sheng Lin and Hsiang-Yao Hsiao from the Lulin Observatory, and we thank Jhen-kuei Guo and Neelam Panwar for coordinating observations at the Tenagra II Observatory. JGC and BS are grateful to NSF grant AST-0908139 for partial support. Support for MC is provided by the Ministry for the Economy, Development, and Tourism's Programa Inicativa Científica Milenio through grant P07-021-F, awarded to The Milky Way Millennium Nucleus; by Proyecto Basal PFB-06/2007; by FONDAP Centro de Astrofísica 15010003; by Proyecto FONDECYT Regular #1110326; and by Proyecto Anillo ACT-86. The authors gratefully acknowledge the entire Kepler team,whose outstanding efforts have made these results possible.
Published - Guggenberger2012p19186Mon_Not_R_Astron_Soc.pdf
Accepted Version - 1205.1344.pdf
Supplemental Material - MNR_21244_sm_Table1.zip