Evidence in Support of a Rotational Model for the Pulsar PSR 0833–45

Radhakrishnan, V.; Cooke, David J.; Komesaroff, M. M.; Morris, David J.

doi:10.1038/221443a0

Cited by 156 publications

(100 citation statements)

References 12 publications

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“…When we observe a beam symmetric about this axis the pulse profile should have its mid-point exactly at the centre of the profile. In the Rotating Vector Model (Radhakrishnan & Cooke 1969) the longitude of the maximum gradient in the polarisation position angle (PA) swing occurs at the fiducial plane, and any small (frequency dependent) deviation from this is usually interpreted as an aberration/retardation (A/R) effect (Blaskiewicz et al, 1991). In a tilted geometry we must be careful with our interpretation of both the intensity profile and its relation to the PA swing.…”

Section: The Fiducial Plane In a Tilted Geometrymentioning

confidence: 99%

Pulsar bi-drifting: implications for polar cap geometry

Wright¹,

Weltevrede²

2016

Mon. Not. R. Astron. Soc.

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For many years it has been considered puzzling how pulsar radio emission, supposedly created by a circulating carousel of sub-beams, can produce the driftbands demonstrated by PSR J0815+09, and more recently PSR B1839-04, which simultaneously drift in opposing directions. Here we suggest that the carousels of these pulsars, and hence their beams, are not circular but elliptical with axes tilted with respect to the fiducial plane. We show that certain relatively unusual lines of sight can cause bidrifting to be observed, and a simulation of the two known exemplars is presented. Although bi-drifting is rare, non-circular beams may be common among pulsars and reveal themselves by having profile centroids displaced from the fiducial plane identified by polarisation position angle swings. They may also result in profiles with asymmetric and frequency-dependent component evolution. It is further suggested that the carousels may change their tilt by specific amounts and later reverse them. This may occur suddenly, accompanying a mode change (e.g. PSR B0943+10), or more gradually and short-lived as in "flare" pulsars (e.g. PSR B1859+07). A range of pulsar behaviour (e.g. the shifting drift patterns of PSRs B0818-41 and B0826-34) may also be the result of non-circular carousels with varying orientation. The underlying nature of these carousels -whether they are exclusively generated by polar cap physics or driven by magnetospheric effects -is briefly discussed.

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Section: The Fiducial Plane In a Tilted Geometrymentioning

confidence: 99%

Pulsar bi-drifting: implications for polar cap geometry

Wright¹,

Weltevrede²

2016

Mon. Not. R. Astron. Soc.

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“…The Vela pulsar formed the basis for the rotating vector model (Radhakrishnan & Cooke 1969), which relates the polarization position angle to the rotating dipolar magnetic field of the neutron star. At the pulse centroid, the spin axis, magnetic moment and line of sight are coplanar.…”

Section: Vela Pulsarmentioning

confidence: 99%

Pulsar Jets: Implications for Neutron Star Kicks and Initial Spins

Lai

Chernoff

Cordes

2001

ApJ

264

304

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We study implications for the apparent alignment of the spin axes, proper-motion directions, and polarization vectors of the Crab and Vela pulsars. The spin axes are deduced from recent Chandra X-ray Observatory images that reveal jets and nebular structure having definite symmetry axes. The alignments indicate these pulsars were born either in isolation or with negligible velocity contributions from binary motions. We examine the effects of rotation and the conditions under which spin-kick alignment is produced for various theoretical models of neutron star kicks. If the kick is generated when the neutron star first forms by asymmetric mass ejection or/and neutrino emission, then the alignment requires that the protoneutron star (and hence the precollapse stellar core) possesses an original spin with period P s much less than the kick timescale τ kick , thus spin-averaging the kick forces on the star. The kick timescale ranges from 100 ms to 10 seconds depending on whether the kick is hydrodynamically driven or neutrino-magnetic field driven. For hydrodynamical models, spin-kick alignment further requires the rotation period of an asymmetry pattern at the radius near shock breakout ( > ∼ 100 km) to be much less than τ kick < ∼ 100 ms; this is difficult to satisfy unless rotation plays a dynamically important role in the core collapse and explosion (corresponding to P s < ∼ 1 ms). Aligned kick and spin vectors are inherent to the slow process of asymmetric electromagnetic radiation from an off-centered magnetic dipole. We reassess the viability of this electromagnetic rocket effect, correcting a factor of 4 error in Harrison and Tademaru's calculation that increases the size of the effect. To produce a kick velocity of order a few hundred km s −1 requires that the neutron star be born with an initial spin close to one millisecond and that spindown due to r-mode driven gravitational radiation be inefficient compared to standard magnetic braking.

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“…The evidence in favor of emission from dipole-like field lines originating from the polar cap includes the sweep of the linear polarization and the variation of the pulse width with period P. The sweep of the linear polarization is consistent with the rotating vector model (Radhakrishnan and Cooke 1969), modified by jumps between orthogonal modes in a broad class of pulsars (Stinebring et al 1984). The statistical dependence (Rankin 1990), W ex l / P 1 / 2 s i n a , of the pulse width on P and a, which is the angle between the rotation and the dipole axes, suggests a source region located near the last closed dipolar field line.…”

Section: Identification Of T H E Emission M E C H a N I S Mmentioning

confidence: 49%