Application of theoretical UBVRI color-color diagrams to colorimetric analyses of various astrophysical objects

UBVRI color indices have been calculated for various kinds of radiation: bl ackbody radiation, radiation of hydrogen plasma that is both optically thin and optically thick in the Balmer continuum, radiation df the upper photos pheres of dwarfs heated by a stationary flow of high-energy particles, sync hrotron radiation, and the radiation of main-sequence stars. The results ar e presented in the form of four color-color diagrams: (U-B)-(B-V), (U-B)-(V -R), (U-B)-(V-I), and (B-V)-(V-R).