Glitches in Pulsars

The effect of an unmodelled glitch in the timing residuals of a pulsar
The effect of an unmodelled glitch in the timing residuals of a pulsar the residuals are flat until the glitch occurs at which point they drift rapidly into positive values. Credit: Espinoza et al (2014)

Glitches are sudden changes (usually increases) to the spin rate (the period) of the pulsar. Glitches are usually followed by quasi-exponential recoveries back towards* the initial spin rate. The phenomenon is generally more common in younger pulsars.

The exact mechanism by which glitches occur is not well understood however they are thought to be due to the crust of the neutron star rotating at a slow rate compared with the superfluid interior. Occasionally, the interior couples to the inner crust and spins the star up abruptly.

Unmodelled glitches cause the residuals to drift away from zero, following a quadratic signature.  Some pulsars never recover their initial spin-rates following a glitch. Less commonly, a pulsar will 'over-recover', ending up with a longer period than it started with.

  • Glitch Catalogue

    The catalogue contains basic glitch information on all published glitches plus regularly updated detections using the Lovell telescope at Jodrell Bank Observatory (Link the catalogue).

    • For each glitch, its epoch and the frequency and frequency derivative fractional steps are given. Epochs are given in Modified Julian Days (MJD), frequency fractional steps are given in units of 10-9 and frequency derivative fractional steps in units of 10-3. The last column of the table indicates the origin of the values and whether the glitch appears in other publications.
    • Unless otherwise stated in the last column, values in the table are estimated as described in Espinoza et al. (2011).
    • You can also access the original table from the paper. This (online) version includes two extra columns containing the frequency jumps (in micro Hz) used for the calculations in the paper and the frequency derivative jumps (in units of 10-15 Hz s-1).
    • We use the definition of glitch given in Espinoza et al. (2011).
  • Crab Nebula Pulsar

    The Crab Nebula pulsar (PSR B0531+21) is the youngest known pulsar, born in a supernova recorded by Chinese astronomers in A.D. 1054, and has been observed at Jodrell Bank since its discovery in 1968. The Crab is currently monitored on a daily basis by the Lovell telescope and the 42-ft telescope at Jodrell Bank Observatory. Reasons for such great interest in this pulsar are:

    Glitches

    The Crab nebula pulsar experiences sudden changes in its spin parameters known as timing glitches, which give valuable clues to the nature of the neutron star interior.

    Giant Pulses

    The Crab emits occaisional 'giant pulses' - pulses up to 1000 times brighter than a normal pulse. This phenomenon is of great interest to those working on the emission physics of pulsars, and allows us to study individual extremely high signal-to-noise pulses.

    Dispersion

    Electron population of the Crab Nebula along the line of sight to the pulsar disperses the emitted radio pulses, causing a frequency-dependent delay to the received signal. By observing the Crab at well-separated frequencies, the nebula environment can be probed.

    Scattering

    Electron number density variations along the line of sight scatter the radio pulses from the Crab, distorting the observed pulse shape.

    Crab Pulsar Monthly Ephemeris

    Glitches and dispersion measure variations are accounted for by using a catalogue of ephemerides for the Crab pulsar.

    For Crab pulsar information, please contact James McKee or Andrew Lyne.

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