Discovery of X-ray pulsations from the compact central source in the supernova remnant 3C 58

We report on high time and spatial resolution observations of the supernova remnant (SNR) 3C 58 using the High Resolution Camera (HRC) on the Chandra X-Ray Observatory. These data show a pointlike central source from which we detect 65.68 ms pulsations at 6.7 sigma significance. We interpret these pulsations as corresponding to a young rotation-powered pulsar, PSR J0205+ 6449, that is associated with and powers SNR 3C 58. Analysis of archival Rossi X-Ray Timing Explorer ( RXTE) data from 3 years earlier confirms these pulsations and allows us to determine a spin-down rate of (P) over dot = 1.93 x 10(-13) s s(-1). Assuming a magnetic dipole model for PSR J0205+ 6449, we infer a surface magnetic field of 3.6 x 10(12) G. The historical age for the pulsar (based on its identification with SN 1181) is 820 yr. Taken with the observed period and spin-down rate, we derive an initial spin period of similar to60 ms.