THIRD LIGHT IN SS433 ACCORDING TO UBVRcIc PHOTOMETRY

UBVRcIc observations of microquasar SS 433 from 1980 to 2023 revealed a stable effect unusual for classical eclipsing binary systems. In the phases of maximum accretion disk opening, the depths of the primary and secondary eclipsing minima of the orbital light curve decrease synchronously with increasing wavelength. To explain this effect, we have used the model of an eclipsing binary system in which there is a third non- eclipsing light. We show that the main source of the third light at a mass-loss rate of 10−4 𝑀⊙/year from the system is the outer semitransparent regions of the supercritical accretion disk, as well as the extended part of the disk wind. The contribution of the non-eclipsed third light increases from 15% in the 𝐵 filter to 40% in the 𝐼𝑐 filter. The interstellar absorption-corrected emission spectrum of the third non-eclipsed light in the range 4000–8000 Å can be described by a power law with an exponent on the wavelength close to −1. Significant changes in system’s light out of eclipses are mainly due not to the classical effect of the ellipticity of the components, but to the variable absorption of light from the components in the common shell around the system formed by powerful winds from the supercritical accretion disk and the donor star.

SS 433, individual stars, SS 433, close binary eclipsing stars, accretion disks