On the location of the oscillations in AE Aquarii
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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 -ray bands, the origin of these 33 s oscillations remains poorly understood. Recent work by Robinson, Shafter, and Balachandran revealed a very puzzling result: the oscillation time-delay curve is phase shifted by 60 with respect to the emission-line radial velocity curve, although both should track the orbital motion of the white dwarf. In this Letter we present simultaneous absorption 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 75, and hence are unreliable tracers of the orbital motion of the white dwarf. However, the oscillation orbit is shifted by only 5 3, confirming that the oscillations arise from a region concentric with the white dwarf. Thus the arrival times of the oscillations yield a measure of the white dwarf's apparent orbital velocity, independent of emission-line radial velocity measurements. Using RSB's value of Kpulse 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 0.91, 0.49 < M2/M 0.70, and 56 i < 70.
