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

We present results of the timing observations of the 143 ms pulsar PSR J0538+2817 that provide a proper-motion measurement clearly showing an association of 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 ± 4 kyr, which is a factor of 20 times less than the pulsar's characteristic age of τ _c = 620 kyr. This age implies an initial spin period of 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.