Analysis of the Kepler \delta Sct star KIC 7106205 showed amplitude modulation in a single pressure mode , whilst all other pressure and gravity modes remained stable in amplitude and phase over the 1470 d length of the dataset .
The Kepler dataset was divided into a series with time bins of equal length for which consecutive Fourier transforms were calculated .
An optimum fixed frequency , calculated from a least-squares fit of all data , allowed amplitude and phase of each pulsation mode for each time bin to be tracked .
The single pressure mode at \nu = 13.3942 d ^ { -1 } changed significantly in amplitude , from 5.16 \pm 0.03 to 0.53 \pm 0.06 mmag , but also varied quasi-sinusoidally in phase , with a characteristic period similar to the length of the dataset .
All other p and g modes were stable in both amplitude and phase , which is clear evidence that the visible pulsation mode energy is not conserved within this star .
Possible causes of the observed amplitude and phase modulation and the missing mode energy are discussed .