ON THE LOCATION OF THE OSCILLATIONS IN AE AQUARII

There is much recent interest on the nature of the oscillations in the cataclysmic variable AE Aquarii. Detected in the optical, UV, X-ray, and possibly gamma-ray bands, the origin of these 33 s oscillations re mains poorly understood. Recent work by Robinson, Shafter, and Balacha ndran revealed a very puzzling result: the oscillation time-delay curv e is phase shifted by approximately 60-degrees with respect to the emi ssion-line radial velocity curve, although both should track the orbit al motion of the white dwarf. In this Letter we present simultaneous a bsorption and emission-line radial velocities, and from the absorption lines we derive an improved ephemeris. We find that our emission-line velocities are phase shifted by approximately 75-degrees, and hence a re unreliable tracers of the orbital motion of the white dwarf. Howeve r, the oscillation orbit is shifted by only 5-degrees +/- 3-degrees, c onfirming that the oscillations arise from a region concentric with th e white dwarf. Thus the arrival times of the oscillations yield a meas ure of the white dwarfs apparent orbital velocity, independent of emis sion-line radial velocity measurements. Using RSB's value of K(pulse) as K1 we find q = M2/M1 = 0.773 +/- 0.026 and M1 sin3 i = 0.528 +/- 0. 017 M., giving masses 0.64 < M1/M. less-than-or-equal-to 0.91, 0.49 < M2/M. less-than-or-equal-to 0.70, and 56-degrees less-than-or-equal-to i < 70-degrees.