The slow rise and recovery of the 2019 Crab pulsar glitch

We present updated measurements of the Crab pulsar glitch of 2019 July 23 using a data set of pulse arrival times spanning ∼5 months. On MJD 58687, the pulsar underwent its seventh largest glitch observed to date, characterized by an instantaneous spin-up of ∼1 μHz. Following the glitch, the pulsar’s rotation frequency relaxed exponentially towards pre-glitch values over a time-scale of approximately 1 week, resulting in a permanent frequency increment of ∼0.5 μHz. Due to our semicontinuous monitoring of the Crab pulsar, we were able to partially resolve a fraction of the total spin-up. This delayed spin-up occurred exponentially over a time-scale of ∼18 h. This is the sixth Crab pulsar glitch for which part of the initial rise was resolved in time and this phenomenon has not been observed in any other glitching pulsars, offering a unique opportunity to study the microphysical processes governing interactions between the neutron star interior and the crust.