Resonances as the general cause of the outbursts in the symbiotic system AG Draconis

The general behaviour of the symbiotic system AG Dra is studied in the cont ext of the long-term photometry monitoring and radial velocity analysis. Pe riod analysis of the data gave two values of periods, 549.(d)73 +/- 1.(d)59 and 355.(d)27 +/- 1.(d)82 days for orbital motion and pulsations of cool g iant respectively. The new orbital elements have been determined as well as the new orbital and pulsation ephemerides respectively. The ratio of the o rbital to the pulsation period is actually very close to 14/9, so resonance might occur. We suggested, that this is the general cause of the recurrenc e time of the active stages. The pulsations of the cool component are very probably non-radial, so accretion by the white dwarf is particularly high w hen the material ejected due to the pulsations, is ejected in certain direc tions with respect to the line joining the two stars. The manifestations of this phenomena are the observed outburst themselves.