The origin of the supersoft X-ray-optical/UV flux anticorrelation in the symbiotic binary AG Draconis

Context. AG Draconis produces a strong supersoft X-ray emission. The X-ray and optical/UV fluxes are in strict anticorrelation throughout the active and quiescent phases. Aims. We identify the source of the X-ray emission and reveal the nature of the observed flux anticorrelation. Methods. We used X-ray and UV observations with XMM-Newton, far-UV spectroscopy from FUSE, low- and high-resolution IUE spectra, and optical/near-IR spectroscopic and/or photometric observations. We modeled the spectral energy distribution and broad wings of the O v