We report results of RXTE observations of PSR B1951+32 using the PCA instrument for 19k seconds during 1996 March 24th .
We applied the contemporaneous radio ephemeris and various statistical tests to search for evidence of pulsation .
These analyses yield intriguing yet inconclusive evidence for the presence of the pulsation in the time series : confidence level for the presence of pulsation is 94.5 % in the 2.0-4.8 keV band and 97.6 % in the 4.8-6.3 keV band based on the H -test .
Under the premise of non-detection of pulsation , we derive estimated 2- \sigma upper limits for the pulsed flux to be 3.3 \times 10 ^ { -6 } { cm } ^ { -2 } { s } ^ { -1 } { keV } ^ { -1 } in the 2.0-4.8 keV band , 2.7 \times 10 ^ { -6 } { cm } ^ { -2 } { s } ^ { -1 } { keV } ^ { -1 } in the 4.8-8.5 keV band , and 2.0 \times 10 ^ { -6 } { cm } ^ { -2 } { s } ^ { -1 } { keV } ^ { -1 } in the 8.5-13.0 keV band .
These upper limits are consistent with the trend of spectral turn-over from high-energy gamma-ray emission as suggested by the OSSE upper limit .
Such turn-over strongly suggests the outer magnetosphere as the emission site for pulsed gamma-rays .
These RXTE upper limits for X-ray pulsation are , on the other hand , not consistent with the extrapolation of reported power-law spectra from the point source observed by ROSAT in the 0.1-2.4 keV band , assuming a constant pulse fraction : The pulsed soft X-ray emission detected by ROSAT must follow a much softer spectrum than that of the overall point source .