Disk-assisted spin-down of young radio pulsars

We present a model for the spin-down of young radio pulsars in which the neutron star loses rotational energy not only by emitting magnetic dipole radiation but also by torquing a surrounding disk produced by supernova fallback. The braking index predicted in our model is, in general, less than n = 3 (the value for pure magnetic dipole radiation), in agreement with the reported values of n < 3 for five young radio pulsars. With an accuracy of 30% or better, our model reproduces the age, braking index, and third-frequency derivative of the Crab pulsar for a disk mass inflow rate in the range of 3 × 10¹⁶-10¹⁷ g s^-1.