The CoRoT star 105288363: strong cycle to cycle changes of the Blazhko modulation

TL;DR

This study analyzes the CoRoT star 105288363, revealing strong cycle-to-cycle changes in its Blazhko modulation, including amplitude and phase variations, using high-precision space-based photometry and Fourier analysis.

Contribution

It provides detailed insights into the long-term variability and stability of the Blazhko cycle in a RR Lyrae star with unprecedented data quality.

Findings

Detected an independent mode with a 0.59 frequency ratio to the fundamental.

Observed strong, independent cycle-to-cycle changes in amplitude and phase modulation.

Found that the phasing between amplitude and phase modulation varies over time.

Abstract

We present the analysis of the CoRoT star 105288363, a new Blazhko RR Lyrae star of type RRab (f0 = 1.7623 c/d), observed with the CoRoT space craft during the second long run in direction of the galactic center (LRc02, time base 145 d). The CoRoT data are characterized by an excellent time sampling and a low noise amplitude of 0.07 mmag in the 2-12 c/d range and allow us to study not only the fine details of the variability of the star but also long-term changes in the pulsation behaviour and the stability of the Blazhko cycle. We use, among other methods, standard Fourier analysis techniques and O-C diagrams to investigate the pulsational behavior of the Blazhko star 105288363. In addition to the frequency pattern expected for a Blazhko RR Lyrae star, we find an independent mode (f1 = 2.984 c/d) showing a f0/f1 ratio of 0.59 which is similar to that observed in other Blazhko RR Lyrae stars. The bump and hump phenomena are also analysed, with their variations over the Blazhko cycle. We carefully investigated the strong cycle-to-cycle changes in the Blazhko modulation (PB = 35.6 d), which seem to happen independently and partly diametrically in the amplitude and the phase modulation. Furthermore, the phasing between the two types of modulation is found to change during the course of the observations.