Simultaneous X-ray, optical and infrared observations of X-ray binaries.

Results of simultaneous X-ray, optical, and IR observations of X-ray binaries are discussed. Observations of A 0535 + 26 were made in a cooperative program including the Astron satellite, the Central Astronomical Observatory at Pulkovo, the Astronomical Observatory of Leningrad University, the Crimean Astrophysical Observatory, the Japanese satellites Hakucho and Tenma, and IUE. One finding is that near-IR photometry can serve to detect hot X-ray coronas in accreting binary systems.