Proper motion, age and initial spin period of PSR J0538+2817 in S147

We present results of timing observations of the 143-ms pulsar J0538+2817 that provide a proper motion measurement which clearly associates the pulsar with the supernova remnant S147. We measure a proper motion of 67${}_{-22}^{+48}$ mas yr${}^{-1}$, implying a transverse velocity of $v=385_{-130}^{+260}$ km s${}^{-1}$. We derive an age of the pulsar and S147 of only $30\pm 4$ kyr which is a factor of 20 times less than the pulsar’s characteristic age of $\tau_c = 620$kyr\mathrm{.}Thisageimpliesaninitialspinperiodof$P_0=139$ ms, close to the present pulse period and a factor of several larger than what is usually inferred for birth periods. Implications for recent X-ray detections of this pulsar are discussed.