Ultraviolet photometry from the orbiting Astronomical Observatory. IX - The ultraviolet behavior of U Ophiuchi

Seven simultaneous light curves of U Oph have been obtained which cover a wavelength range from the blue part of the optical spectrum to just longward of L alpha in the ultraviolet. An analysis of these curves has been carried out to determine the spectral variation of limb and gravity darkening as well as to determine geometrical elements for the system. We conclude that (1) U Oph is gravity darkened to the extent expected from von Zeipel's law, (2) limb darkening increases toward shorter wavelengths, and (3) at the shortest wavelengths observed, the two stars are limb-darkened totally.