On the aberration-retardation effects in pulsars

Abstract

The magnetospheric locations of pulsar radio emission region are not well known. The actual form of the so-called radius-to-frequency mapping should be reflected in the aberrationretardation (A/R) effects that shift and/or delay the photons depending on the emission height in the magnetosphere. Recent studies suggest that in a handful of pulsars the A/R effect can be discerned with respect to the peak of the central core emission region. To verify these effects in an ensemble of pulsars, we launched a project analysing multifrequency total intensity pulsar profiles obtained from the new observations from the Giant Meterwave Radio Telescope (GMRT), Arecibo Observatory (AO) and archival European Pulsar Network (EPN) data. For all these profiles, we measure the shift of the outer cone components with respect to the core component, which is necessary for establishing the A/R effect. Within our sample of 23 pulsars, seven show the A/R effects, 12 of them (doubtful cases) show a tendency towards this effect, while the remaining four are obvious counterexamples. The counterexamples and doubtful cases may arise from uncertainties in the determination of the location of the meridional plane and/or the core emission component. Hence, it appears that the A/R effects are likely to operate in most pulsars from our sample. We conclude that in cases where those effects are present the core emission has to originate below the conal emission region.

Meterwavelength Single-pulse Polarimetric Emission Survey. III. The Phenomenon of Nulling in Pulsars

“…Several observational evidence suggest that the radio emission arises around 500 kilometers above the neutron star due to coherent curvature radiation (Mitra & Rankin 2002;Kijak & Gil 2003;Mitra & Li 2004;Krzeszowski et al 2009;Mitra et al 2009). These basic observational features can be best explained by the so called steady state polar cap models (e.g., Sturrock 1971;Ruderman & Sutherland 1975).…”

Rotational asymmetry of pulsar profiles

“…Gangadhara & Gupta (2001, hereafter GG01), noted that profiles of selected pulsars have outer cones more shifted towards early phase than inner cones. Krzeszowski et al (2009) find at least a tendency towards this effect in most pulsars in their sample, but they also find some counterexamples (e.g. B1831−04).…”

Absolute emission altitude of pulsars: PSRs B1839+09, B1916+14, and B2111+46

“…But the retardation phase shift was ignored in BCW91, as they assumed a constant emission height across the pulse. In GG01, GG03, Johnston & Weisberg (2006) and Krzeszowski et al (2009) it was shown though that the emission altitude is not constant across the pulse, and hence retardation has to be taken into account while estimating the A/R phase shifts. Further, showed that the centroid of the intensity profile advances by ∼2 r/r LC while the PPAIP is delayed by ∼2 r/r LC due to A/R effects with respect to the meridional plane.…”

“…The results of this purely geometric method are found to be in rough agreement with those of BCW91. However, the relativistic phase shift method clearly indicates that the emission altitude across the pulse window is not constant (GG01; GG03; DRH04; Johnston & Weisberg 2006;Krzeszowski et al 2009). …”