We investigated magnetic variability of the roAp star gamma Equ (HD 201601) with high time resolution. Measurements of the stellar longitudinal magnetic field B_e were performed with the hydrogen line polarimeter and the 6-m optical telescope of Special Astrophysical Observatory on 20/21 August 1989. We obtained a single 3-hour series of 1720 rapid B_e measurements for this star with the average time resolution of 6.6 sec. The averaged value of <B_e> on this night equals -750 pm 22 G. Both the power spectrum and the amplitude spectrum of the B_e time series essentially are flat. However, they show the presence of a marginally significant magnetic period at P_B = 3.596 min. which is real with the probability 67 %. The amplitude of the magnetic field variations with this period equals 347 pm 31 G. We did not detect variations of B_e field in gamma Equ with the well-known photometric period, P_phot=12.44 min.
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