Secular variability of the longitudinal magnetic field of the Ap star gamma Equ

Abstract

We present an analysis of the secular variability of the longitudinal magnetic field B_e in the roAp star gamma Equ (HD 201601). Measurements of the stellar magnetic field B_e were mostly compiled from the literature, and append also our 33 new B_e measurements which were obtained with the 1-m optical telescope of Special Astrophysical Observatory (Russia). All the available data cover the time period of 58 years, and include both phases of the maximum and minimum B_e. We determined that the period of the long-term magnetic B_e variations equals 91.1 +/- 3.6 years, with B_e (max) = + 577 +/- 31 G and B_e (min) = -1101 +/- 31 G.

5 pages, 2 figures, accepted to MNRAS