We present the analysis of the CoRoT star 105288363 , a new Blazhko RR Lyrae star of type RRab ( f _ { 0 } = 1.7623 d ^ { -1 } ) , 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 d ^ { -1 } 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 ( f _ { 1 } = 2.984 d ^ { -1 } ) showing a f _ { 0 } / f _ { 1 } 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 ( P _ { B } = 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 .