A multisite campaign of the rapid rotator in the Praesepe cluster, BU Cnc = KW 207, was undertaken at five observatories (Sierra Nevada, Devon, Xing-Long, Lowell and Piszekesteto observatories). The existence of four pulsation modes with frequencies of 19.76, 17.36, 16.69, and 18.62 cycles per day can be regarded as definite, while the existence of two further modes at 19.87 and 23.91 cycles per day is very probable. The signal/noise ratios of these frequencies in the Fourier amplitude spectrum range from 9 to 18 for the four primary frequencies and between 4 and 5 for the next two frequencies. The solution fits the observations to 2.6 millimag.
Purely radial pulsation can be excluded due to the high ratios between the values of adjacent frequencies. The Q values of the pulsation modes range from 0.015 to 0.021 days. The modes can be identified with p3˜1 modes with at least two different l modes.
The diagram shows the power spectrum of BU Cnc for the new measurements. Note the simple spectral window resulting from the multisite coverage. With one cycle per day aliasing the frequencies probably would not have been found.
A manuscript by Breger, Stich, Garrido, Martin, Jiang, Li, Ostermann, Scheck and Paparo is being submitted to Astron. Astrophys.
Power spectrum of BU Cnc for the new multisite measurements made by the Delta Scuti Network. The spectra are shown before and after applying multiple-frequency solutions.