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Keywords:

  • polarization;
  • radiation mechanisms: non-thermal;
  • pulsars: general;
  • pulsars: individual: J1119−6127

ABSTRACT

Rotation-powered radio pulsars are generally observed to pulse regularly in the radio band, but this is not the case for so-called rotating radio transients (RRATs) which emit only sporadic bursts of radio emission. We demonstrate that the high-magnetic field pulsar J1119−6127 exhibits three different types of behaviour in the radio band. Trailing the ‘normal’ profile peak there is an ‘intermittent’ peak and these components are flanked by two additional components showing very erratic ‘RRAT-like’ emission. Both the intermittent and RRAT-like events are extremely rare and are preceded by a large amplitude glitch in the spin-down parameters. The post-glitch relaxation occurs on two different time-scales (20 and 210 d) and the post-glitch spin-down rate is smaller than the pre-glitch rate. This type of relaxation is also seen in an earlier, smaller glitch and is very unusual for the pulsar population as a whole, but is observed in the glitch recovery of an RRAT. The abnormal emission behaviour in PSR J1119−6127 was observed up to three months after the epoch of the large glitch, suggestive of changes in the magnetospheric conditions during the fast part of the recovery process. We argue that both the anomalous recoveries and the emission changes could be related to reconfigurations of the magnetic field. Apart from the glitches, the spin-down of PSR J1119−6127 is relatively stable, allowing us to refine the measurement of the braking index (n= 2.684 ± 0.002) using more than 12 yr of timing data.

The properties of this pulsar are discussed in light of the growing evidence that RRATs do not form a distinct class of pulsar, but rather are a combination of different extreme emission types seen in other neutron stars. Different sub-classes of the RRATs can potentially be separated by calculating the lower limit on the modulation index of their emission. Unlike other quantities, this parameter is independent of observation duration allowing a direct comparison with other emission phenomena. We speculate that if the abnormal behaviour in PSR J1119−6127 is indeed glitch induced then there might exist a population of neutron stars which only become visible in the radio band for a short duration in the immediate aftermath of glitch activity. These neutron stars will be visible in the radio band as sources that only emit a cluster of pulses once every few years.