SIMBAD references

We present new X-ray timing and spectral observations of PSR J1930+1852, the young energetic pulsar at the center of the nonthermal 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 P{dot}=7.5112(6)x10^–13 s/s, suggesting strong timing noise and/or glitch activity. The X-ray emission is highly pulsed (71%±5% modulation) and is characterized by an asymmetric, broad profile (∼70% duty cycle) that is nearly twice the radio width. The spectrum of the pulsed emission is well fitted with an absorbed power law of photon index Γ=1.2±0.2; this is marginally harder than that of the unpulsed component. The total 2-10 keV flux of the pulsar is 1.7x10^–12 ergs/cm2/s. These results confirm PSR J1930+1852 as a typical Crab-like pulsar.