|11th of May 2018|
|Catching a Vela glitch|
As pulsars, rapidly rotating neutron stars, lose energy,
their rotation slows down. However, for some pulsars
this spin-down is interrupted by occasional abrupt spin-up events
known as glitches.
A glitch appears as a small change in the rotation rate of the neutron
star and its co-rotating magnetosphere, which is revealed by an abrupt
change in the timing of the arrival of observed radio pulses.
High time resolution measurements of the flux density, polarization
and single-pulse arrival times before, during, and after the glitch
may reveal clues as to the mechanism behind this phenomenon.
This has not previously been
possible because glitches happen unpredictably.
Palfreyman et al. have recently reported single-pulse radio observations of a glitch in the Vela pulsar, which rorates 11.2 times per second. The glitch was detected on 2016 December 12, during continuous observations of the pulsar over a period of three years. As illustrated in the figure above, sudden changes in the pulse shape coincident with the glitch event were detected: one pulse was unusually broad, the next pulse was missing (a ‘null’) and the following two pulses had unexpectedly low linear polarization. This sequence was followed by a 2.6-second interval during which pulses arrived later than usual, indicating that the glitch had affected the magnetosphere. The left panels show the total flux density in arbitrary units, the middle panels show linear polarization and the right panels show the position angle of the linear polarization.