Figure 1.

Upper frame, a sample light curve of white-light CBA photometry. Each point is a 60-s integration. The 525 s variations are occasionally but barely visible in the raw light curve. Middle frame, power spectrum of the 1997 light curve. Significant peaks are marked with their period in seconds. The signals at 525.65 and 350.43 s are just the usual harmonics of the main signal, but the signal at 1028.74 s appears to be a new feature. Lower left frame, 1997 light curve summed at 1051.30 s. The double-humped waveform agrees in detail with all previous studies, indicating that 1051.3 s is indeed the fundamental period of the main signal (although most of the power is clearly at the first harmonic, 525 s). Lower right frame, 1997 light curve summed at 1028.733 s.

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