The jets and supercritical accretion disk in SS433

Abstract

The review describes observations and investigations of the unique object SS433 obtained after 23 years of studying this massive binary system. The main difference between SS433 and other known X-ray binaries is the action of a constant supercritical regime for the accretion of gas onto the relativistic star (most likely a black hole), which has lead to the formation of a supercritical accretion disk and collimated relativistic jets. The properties of the jets are, to a large extent, determined by their interaction with the disk wind. The precession of the disk and jets, as well as the eclipsing in the binary system, make SS433 a unique laboratory for studies of mechanisms for the microquasar phenomenon. The review describes the main ideas and results emerging from studies of the formation of the jets and supercritical accretion disk in SS433. Essentially all photometric and spectroscopic properties of SS433 are determined by the accretion disk and its orientation, but the disk itself is not observed, being located beneath the photosphere of the dense wind. Observational manifestations of the wind and of gas flows in the system are described, as well as possible properties of the material lost by the system in its equatorial plane. Little is known about the structure of the central regions where the hot bases of the jets are located immediately above the plane of the disk. The available X-ray, ultraviolet, and optical observations paint a picture in which the bases of the jets are surrounded by cocoons of hot gas reradiating emission from the inner regions of the jet channel. Direct investigations of this channel in the supercritical accretion disk of SS433 are not possible; however, a similar object oriented face-on would likely be an extremely bright X-ray source, such as those observed in other galaxies.