Rossi X-Ray Timing Explorer observation of PSR B0656+14

PSR B0656 + 14 was observed by the Rossi X-Ray Timing Explorer (RXTE) with the proportional counter array (PCA) and the high-energy X-ray timing exper iment (HEXTE) for 160 ks during 1997 August 22-September 3. No pulsation wa s firmly found in the timing analysis, during which the contemporaneous rad io ephemeris and various statistical tests were applied in searching for ev idence of pulsation. A marginal detection of pulsation at a confidence leve l of 95.5% based on the H test was found with data in the: whole HEXTE ener gy band, In the energy band of 2-10 keV the RXTE PCA upper limits are about 1 order of magnitude lower than that from ASCA GIS data. If the Compton Ga mma Ray Observatory EGRET detection of this pulsar is real, considering the common trait that most EGRET-detected pulsars have a cooling spectrum in h ard X-ray and gamma-ray energy bands, the estimated RXTE upper limits indic ate a deviation (low-energy turnover) from a cooling spectrum starting from 20 keV or higher. This in turn suggests an outer magnetospheric synchrotro n radiation origin For high-energy emissions from PSR B0656 + 14. The RXTE PCA upper limits also suggest that a reported power-law component based on ASCA SIS data in 1-10 keV fitted jointly with ROSAT data, if real, should b e mainly unpulsed.