| Popis: |
The 33s.08 oscillation and its second harmonic in the optical light of AE Aqr, detected by Patterson (1979; ApJ 234, 978) and being due to hot magnetic pole caps rotating in and out of sight, are considered a persistent characteristic of the system. Photometry performed over a time base of four weeks in July-August 1993 shows, however, that the oscillations have vanished below a detectable limit (see also Bruch et ah 1994; IBVS 3996). Power spectra of the light curves show neither a coherent signal at 33s.08 or 15s.54 nor QPO around these periods. Tests with tracer signals allowed us to put a conservative upper limit of 0m.005 to the amplitude of any coherent signal in the data. We investigated archive light curves of AE Aqr of 45 nights distributed (unevenly) over the years 1978 – 1992 and found the oscillations to be absent only in one the these nights. A comparable case may be V533 Her where Robinson and Nather (1983; ApJ 373, 255) reported the disappearance of the 63 s periodicity. |
