... SHTOL ' Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz 357147, Russia The investigation of such a phenomenon as the magnetic field variability at long times (years - decennials) is very interesting. If the explanation of the magnetic field variability with rotation period by the oblique rotator model is evident, then the reason of the long-period variability is not clear yet, despite the existence of some assumptions on its nature. ... Fig.2. ... 213 Fig.3. ...

... 458 ­ 461 Magnetic Variability of the Ap Star HD 9996 Bychkov V. D.1 , Bychkova L. V.1 , Madej J.2 , Shatilov A. V.1 1 2 Special Astrophysical Observatory, Nizhny Arkhyz, Russia Warsaw University Observatory, Poland Abstract. ... Its phase magnetic curve exhibits two components. ... 1 Long­Perio d Magnetic Phase Curve Compilation of early photometric measurements of HD 9996 allowed us to constrain the corresponding period P in the range of 7750 < Pph < 8550 days (Pyper & Adelman, 1986). ...