Pulsars associated with supernova remnants ( SNRs ) are valuable because they provide constraints on the mechanism ( s ) of pulsar spin-down .
Here we discuss two SNR/pulsar associations in which the SNR age is much greater than the age of the pulsar obtained by assuming pure magnetic dipole radiation ( MDR ) spin-down .
The PSR B1757 - 24/SNR G5.4 - 1.2 association has a minimum age of \sim 40 kyr from proper motion upper limits , yet the MDR timing age of the pulsar is only 16 kyr , and the newly discovered pulsar PSR J1846 - 0258 in the > 2 kyr old SNR Kes 75 has an MDR timing age of just 0.7 kyr .
These and other pulsar/SNR age discrepancies imply that the pulsar spin-down torque is not due to pure MDR , and we discuss a model for the spin-down of the pulsars similar to the ones recently proposed to explain the spin-down of soft gamma–ray repeaters ( SGRs ) and anomalous x–ray pulsars ( AXPs ) .