1999A&A...348..533G

The general behaviour of the symbiotic system AG Dra is studied in the context of the long-term photometry monitoring and radial velocity analysis. Period analysis of the data gave two values of periods, 549.73±1.59d and 355.27±1.82d days for orbital motion and pulsations of cool giant respectively. The new orbital elements have been determined as well as the new orbital and pulsation ephemerides respectively. The ratio of the orbital 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 recurrence 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 when the material ejected due to the pulsations, is ejected in certain directions with respect to the line joining the two stars. The manifestations of this phenomena are the observed outbursts themselves.