Pulsar Spindown by a Fall-Back Disk and the P-P_dot Diagram

Neutron stars may be surrounded by fall-back disks formed from supernova core-collapse. If the disk circumscribes the light-cylinder, the neutron star will be an active radio pulsar spinning down under the propeller spin-down torque applied by the disk as well as the usual magnetic dipole radiation torque. Evolution across the P-P_dot diagram is very rapid when pulsar spin-down is dominated by the propeller torque. This explains the distribution of pulsars in the P-P_dot diagram.