No persistent pulsations in Aquila X-1 as it fades into quiescence

We searched for coherent X-ray pulsations from Aql X-1 in a series of RXTE observations taken shortly after a recent outburst. During the course of th ese observations, Aql X-1 passes through an apparent "propeller" II phase a s its luminosity fades to its quiescent value. No pulsations were detected, and we place upper limits (ranging from 0.52% to 9.0%) on the fractional r ms amplitude of any periodic signal contained in the various data sets sear ched. This result has implications for the geometry of the system, if the q uiescent luminosity is due to continued low-level accretion. Alternatively, our result supports the idea that the quiescent luminosity may be due to t hermal emission.