We present new X-ray timing and spectral observations of PSR J1930 + 1852 , the young energetic pulsar at the center of the non-thermal supernova remnant G54.1 + 0.3 .
Using data obtained with the Rossi X-ray Timing Explorer ( RXTE ) and Chandra X-ray observatories we have derived an updated timing ephemeris of the 136 ms pulsar spanning 6 years .
During this interval , however , the period evolution shows significant variability from the best fit constant spin-down rate of \dot { P } = 7.5112 ( 6 ) \times 10 ^ { -13 } s s ^ { -1 } , suggesting strong timing noise and/or glitch activity .
The X-ray emission is highly pulsed ( 71 \pm 5 \% modulation ) and is characterized by an asymmetric , broad profile ( \sim 70 \% duty cycle ) which is nearly twice the radio width .
The spectrum of the pulsed emission is well fitted with an absorbed power law of photon index \Gamma = 1.2 \pm 0.2 ; this is marginally harder than that of the unpulsed component .
The total 2 - 10 keV flux of the pulsar is 1.7 \times 10 ^ { -12 } erg cm ^ { -2 } s ^ { -1 } .
These results confirm PSR J1930 + 1852 as a typical Crab-like pulsar .