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Intermittent

The P863 project (intermittent pulsars)

The Parkes P863 project started in April 2014 and is ongoing. The primary goal is to analyse the properties of state switching pulsars over long time intervals. Decoding stellar magnetospheres is key to explaining the coherent radio emission observed from planets, brown dwarfs, main-sequence stars, pulsars and radio transient events. Our project attempts to study perhaps the most complex radio emission process - the emission from radio pulsars.

Pulsars are strange objects. Some undergo "glitch events" during which the pulsar's spin frequency dramatically increases. Individual pulses from pulsars vary in shape and brightness. Some can be completely missing (known as "nulling") and pulse components can drift in pulse phase ("sub-pulse drifting"). On time scales of hours to years, pulsars are known to simply switch off. Such pulsars are known as "intermittent" pulsars. On similar time scales pulsars are known to "mode" in which their profile suddenly changes between a few well-defined states. Over time scales of months to years the observations of a few pulsars have been modelled assuming that the neutron star is undergoing free-precession. An analysis of observations of pulsars over many decades have shown that the pulse arrival times follow a red-noise random process (known as timing noise). All these phenomena were originally thought to be unrelated, but we now have evidence showing that they may all be linked.

Our observations are being obtained with the Parkes radio telescope in order to carry out an in-depth study of state-changing pulsars in order to search (and study) links between the various phenomena described above.

Some results 1

Observations of the intermittent pulsar PSR J1717-4054. The top panel shows the pulse profile. The middle panel shows the pulse profile (displayed using the colour scale) as a function of pulse phase and time. The bottom panel is the same, but the profile is shown as a function of frequency. The middle panel shows that the pulse was bright for the first ~3 minutes of the observation and then abruptly switched off.

We now have a large number of observations of this pulsar from the P863 and the PULSE@Parkes observing projects. We have already published one paper on this pulsar (Kerr et al. 2014) and expect to publish more details on the long term intermittent behaviour in the near future.

Some results 2

Observations of PSR J1717-4054 as reported by Kerr et al. (2014). This shows every pulse from the pulsar over 9.5 hours. The significance of a single pulse detection is shown on the y-axis. Points in green indicate when the pulsar is "on". Blue points indicate RFI. Red points are when the pulsar is "off".

The P863 sample contains multiple intermittent pulsars. The state-changing time scale varies for different pulsars with some pulsars having an on-off time scale measured in years.

Some results 3

Observations of PSR J1107-5907 as reported by Hobbs et al. (2016). The two panels represent two different observing bands. The numbers indicate regions in which the pulse spectral index is clearly different.

We have simultaneous ASKAP observations of this pulsar with the P863 data. Combining the data sets together we can study the long term emission properties. This pulsar is thought to have three emission states, but recent work has suggested that there are only two states. Our data can be used to resolve this problem.

Team

  • George Hobbs, PI
  • Matthew Kerr
  • Ryan Shannon
  • Vikram Ravi
  • Simon Johnston
  • Robert Hollow
  • Shi Dai
  • Charlotte Ward
  • Aaron Annuscheit
  • Rai Yuen

We welcome new members to join the project.

Pulsars

PulsarNotes
J0742-2822Correlation found between pulse shape and spin-down rate after a glitch event had occurred
J0828-3417Strong bursts of pulses followed by a very weak state
J1107-5907Exhibits three modes (strong, weak and off)
J1634-5107Intermittent pulsar detected 11% of the time
J1717-4054Intermittent pulsar studied in depth at Parkes
J1830-1059State changing pulsar thought to be undergoing free precession
J1832+0029Intermittent pulsar with a time scale of ~600d on and 800d off
J1841-0500Intermittent pulsar with a time scale of ~400d on and 580d off
J1933+2421Original intermittent pulsar
J1938+2213Strong individual pulses

Data

All data from the P863 project are available from the CSIRO data archive (). They are publically available after 18 months since the observation.

Publications