Abstract

Space photometic results on non-modulated RR Lyrae stars

József Benkõ

MTA CSFK CSI, Hungary

After a brief introduction, in which I show some main features of RR Lyrae stars, I shortly review the former ground-based and space-born light curve stability studies. Then I present our recent results on the Kepler non-Blazhko sample. We analyzed the long and short cadence (LC and SC) light curves of the Kepler non-Blazhko RRab stars. We prepared the Fourier spectra, the Fourier amplitude and phase variation functions, time-frequency representation, the O-C diagrams and their Fourier contents. Our main findings are:
(i) All stars which are brighter a certain magnitude limit show significant cycle-to-cycle (C2C) light curve variations.
(ii) We found permanently excited additional modes for at least one third of the sample and some other stars show temporarily excited additional modes. That is the former hypothesis that additional mode frequencies appear only in Blazhko stars has been rejected. New subharmonic frequency stuctures have been discovered for many stars which have not been identified yet.
(iii) The presence of the Blazhko effect was carefully checked and identified one new Blazhko candidate but for at least 16 stars the effect can be excluded. This shows that the found C2C variation is independent from the Blazhko effect. The connection between the extra modes and the C2C variations is also marginal.