Initial spin periods of neutron stars in supernova remnants

Abstract

We present estimates of initial spin periods, $P_0$, for radio pulsars associated with supernova remnants. By using the published data on 30 objects, we were able to derive a reliable estimate for the initial spin period, assuming standard magneto-dipole spin-down (braking index n=3), in many cases. Our set of estimates is still not sufficient to infer the exact shape of the initial period distribution. However, we show that a gaussian distribution with mean and deviation $\sim 0.1$ s is consistent with our results, while flat, wide distributions and very narrow ones are disfavored.