Pulsars rotate very rapidly and generally slow down as they age, but some pulsars are actually sped up due to interactions with companion stars and become "millisecond pulsars".
Get the rotation period and the corrected period derivative of the pulsars:
In[1]:=
pulsars=EntityValue"Pulsar",
rotationperiod
,
correctedperiodderivative
;
Plot the rotation period versus the period derivative and see the "millisecond pulsars" clustered at the lower left: