Discovery of a 136 millisecond radio and X-ray pulsar in SNR G54.1+0.3
  We report the discovery of a pulsar with period P = 136 ms and dispersion measure 308 pc/cc in a deep observation of the supernova remnant (SNR) G54.1+0.3 with the Arecibo radio telescope. Timing measurements of the new pulsar, J1930+1852, reveal a characteristic age of Pdt/2dP = 2900 yr and spin-down luminosity dE/dt = 1.2e37 erg/s. We have subsequently searched archival ASCA X-ray data of this SNR, and detect pulsations with a consistent period. These findings ensure that PSR J1930+1852 is the pulsar that powers the "Crab-like" SNR G54.1+.3. Together with existing Chandra observations of the SNR, we derive an X-ray pulsed fraction (2-10 keV) of ~27%. We also find that the cooling efficiency of the pulsar wind nebula (PWN) is intermediate between those of the Vela and Crab PWNe: Lx (2-10 keV) ~0.002 dE/dt. PSR J1930+1852 is a very weak radio source, with period-averaged flux density at 1180 MHz of 60 microJy. For a distance of 5 kpc, its luminosity, ~1 mJy kpc^2, is among the lowest for known young pulsars. 
F. Camilo (1), D. R. Lorimer (2), N. D. R. Bhat (3), E. V. Gotthelf   (1), J. P. Halpern (1), Q. D. Wang (4), F. J. Lu (4 an...