A colliding-winds interpretation of the U orbital variation of the symbiotic binary AG Pegasi

The photometric U orbital variations of the symbiotic binary AG Peg, caused by occultation of a bright gaseous region by the M giant in this system, a re used to determine the geometry of this region whose existence is explain ed in the framework of the colliding winds model. The emission of the brigh t region varies and a particular value of its mean density of 2-3 10(10) cm (-3) has been derived. The causes for the irregular variations of the light in the orbital minimum and maximum are discussed. It is also obtained, whe n the mass-loss rate of the hot companion of the system decreases to about 5 10(-10) M-circle dot yr(-1), this bright region will disappear.