Rossi X-ray T Iming Expl Orer Observation of Psr B0656]14

PSR B0656]14 was observed by the Rossi X-Ray T iming Explorer (RXT E) with the proportional counter array (PCA) and the high-energy X-ray timing experiment (HEXTE) for 160 ks during 1997 August 22ÈSeptember 3. No pulsation was Ðrmly found in the timing analysis, during which the contemporaneous radio ephemeris and various statistical tests were applied in searching for evidence of pulsation. A marginal detection of pulsation at a conÐdence level of 95.5% based on the H test was found with data in the whole HEXTE energy band. In the energy band of 2È10 keV the RXT E PCA upper limits are about 1 order of magnitude lower than that from ASCA GIS data. If the Compton Gamma Ray Observatory EGRET detection of this pulsar is real, considering the common trait that most EGRETdetected pulsars have a cooling spectrum in hard X-ray and gamma-ray energy bands, the estimated RXT E upper limits indicate a deviation (low-energy turnover) from a cooling spectrum starting from 20 keV or higher. This in turn suggests an outer magnetospheric synchrotron radiation origin for highenergy emissions from PSR B0656]14. The RXT E PCA upper limits also suggest that a reported power-law component based on ASCA SIS data in 1È10 keV Ðtted jointly with ROSAT data, if real, should be mainly unpulsed. Subject headings : pulsars : individual (PSR B0656]14) È X-rays : stars