Discovery of 2-3s quasi-periodic oscillations in EF Eri.

The AM Her system EF Eri is shown to exhibit optical 2-3-second quasi-periodic oscillations. This is the third AM Her system for which such oscillations have been detected. The discovery of oscillations in EF Eri, which is believed to contain a high-mass (greater than about 1 solar mass) white dwarf, may pose problems for oscillating shock models. The similarity of the magnetic-field orientation in the three systems with known oscillations is pointed out; this could be an indication that the oscillations are instead associated with the magnetic field.