AG Draconis observed with XMM-Newton

Context. AG Draconis is the brightest symbiotic star in X-rays and one of the prototypes of the supersoft X-ray source class. Aims. Study of the X-ray spectrum of this peculiar binary system, covering both quiescence and activity periods, is necessary to investigate the physics of the high temperature spectral component, and to unveil the origin of the outbursts. Methods. X-ray and UV observations with XMM-Newton during 2003–2005 and coordinated optical spectrophotometric monitoring, together with archive data, are employed to derive the behaviour of the high energy source of the AG Dra system during different orbital and activity phases. Results. During quiescence the X-ray emission is very soft and is close in strength to the previous ROSAT observations, with an