# Revisiting the Kepler non-Blazhko RR Lyrae sample: Cycle-to-cyle variations and additional modes

## TL;DR

This study analyzes Kepler non-Blazhko RR Lyrae stars, revealing cycle-to-cycle variations, additional pulsation modes, and clarifying the relationship with the Blazhko effect, challenging previous high incidence claims.

## Contribution

It provides a detailed analysis of light curve variations and additional modes in non-Blazhko RR Lyrae stars, refining understanding of their pulsation behaviors.

## Key findings

- Cycle-to-cycle variations are present in all brighter stars.
- At least one third show permanently excited additional modes.
- The Blazhko effect is less prevalent than previously reported.

## Abstract

We analyzed the long and short cadence 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 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. (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 fact has important consequences. Either the cycle-to-cycle variation phenomenon is independent from the Blazhko effect and the Blazhko incidence ratio is still much lower (51%-55%) than the extremely large (>90%) ratio published recently. The connection between the extra modes and the cycle-to-cycle variations is marginal.