Pulsar B1237 + 25 aberration/retardation analysis from decimetre to decametre wavelength: challenge to ‘radius-to-frequency mapping’

ABSTRACT PSR B1237 + 25 is perhaps the canonical example of a pulsar with a core/double cone profile. Moreover, it is bright with little spectral turnover, and its profile perhaps uniquely remains undistorted by scattering far into the decametric band. Here, we assemble more than a dozen of the highest quality profiles (30 MHz to 5 GHz) from half a dozen observatories, where possible polarimetric. The pulsar’s 2.6$^\circ$ core component marks the magnetic axis longitude, and we confirm that this point coincides both with the linear polarization angle inflection point and the zero-crossing of its antisymmetric circular signature – thus providing the possibility to estimate emission heights over a very broad band using aberration/retardation (A/R). We then carefully fit the profile components with Gaussians to identify and study the subtle asymmetries produced by A/R. We find a consistent A/R in the pulsar’s profiles of some 0.5$^\circ$ longitude or 2 ms – corresponding to a putative conal emission height of 200–400 km – with a formal error of about 100 km. Our analysis finds no evidence whatsoever for an emission height increase with wavelength, the so-called radius-to-frequency mapping. Nor do we find any significant difference in A/R effect between the outer and inner cones.