Time series analysis of infrared circumstellar emission line variability. Shown are the bidimensional periodogram (left), the corresponding line profiles (middle), and the correlation matrices (right). Right panels: the color range corresponds to the normalized power of the period, and the horizontal solid line represents the rotation period of the star, P = 6.53 days. Middle panels: different colors correspond to different rotation cycles: black – cycle 0; green – cycle 1; red – cycle 2; and light blue – cycle 3. Left panels: the color range represents the linear correlation coefficient between different velocity bins of the line profiles. Perfect anticorrelation corresponds to −1 (black), no correlation to 0 (light blue), and perfect correlation to 1 (orange).