Recovery of 29-s Oscillations in HST/FOS Eclipse Observations of the Cataclysmic Variable UX Ursae Majoris

Low amplitude (≃ 0.5%) 29-s oscillations have been detected in HST/FOS eclipse observations of the nova-like cataclysmic variable UX UMa. These are the same dwarf nova-type oscillations that were originally discovered in this system by Warner & Nather in 1972. The 29-s oscillations are seen in one pair of eclipse sequences obtained with the FOS/PRISM in November of 1994, but not in a similar pair obtained with the FOS/G160L grating in August of the same year. The oscillations in the PRISM data are sinusoidal to within the small observational errors and undergo an approximately −360 phase shift during eclipses (i.e. one cycle is lost). Their amplitudes are highest at pre-eclipse orbital phases and exhibit a rather gradual eclipse whose Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-2655