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AK Harding

Publications and source records attributed to AK Harding.

4 recordsLinked to original sources
PubMed2000

High Magnetic Field Pulsars and Magnetars: A Unified Picture.

We propose a unified picture of high magnetic field radio pulsars and magnetars by arguing that they are all rotating high-field neutron stars but that their magnetic axes have different orientations with respect to their rotation axes. In strong magnetic fields where photon splitting suppresses pair creation near the surface, the high-field pulsars can have active inner accelerators while the anomalous X-ray pulsars cannot. This can account for the very different observed emission characteristics of the anomalous X-ray pulsar 1E 2259+586 and the high-field radio pulsar PSR J1814-1744. A predicted consequence of this picture is that radio pulsars having surface magnetic fields greater than about 2x1014 G should not exist.

Journal Article↗
PubMed2000

Radio Pulsar Death Line Revisited: Is PSR J2144-3933 Anomalous?

We reinvestigate the radio pulsar "death lines" within the framework of two different types of the polar cap acceleration models, i.e., the vacuum gap model and the space-charge-limited flow model, with either curvature radiation or inverse Compton scattering photons as the source of pairs. General relativistic frame dragging is taken into account in both models. We find that the inverse Compton scattering-induced space-charge-limited flow model can sustain strong pair production in some long-period pulsars, which allows the newly detected 8.5 s pulsar PSR J2144-3933 to be radio loud without assuming special neutron star equations of state or ad hoc magnetic field configurations.

Journal Article↗
PubMed1999

Magnetar Spin-Down.

We examine the effects of a relativistic wind on the spin-down of a neutron star and apply our results to the study of soft gamma repeaters (SGRs), which are thought to be neutron stars with magnetic fields greater than 1014 G. We derive a spin-down formula that includes torques from both dipole radiation and episodic or continuous particle winds. We find that if SGR 1806-20 puts out a continuous particle wind of 1037 ergs s-1, then the pulsar age is consistent with that of the supernova remnant, but the derived surface dipole magnetic field is only 3x1013 G, in the range of normal radio pulsars. If instead the particle wind flows are episodic with small duty cycle, then the observed period derivatives imply magnetar-strength fields, while still allowing characteristic ages within a factor of 2 of the estimated supernova remnant age. Close monitoring of the periods of SGRs will allow us to establish or place limits on the wind duty cycle and thus the magnetic field and age of the neutron star.

Journal Article↗