2016MNRAS.460.3063M

Radio pulsar B1933+16 is the brightest core-radiation-dominated pulsar in the Arecibo sky, and here we carry out a comprehensive high-resolution polarimetric study of its radiation at both 1.5 and 4.6 GHz. At 1.5 GHz, the polarization is largely compatible with a rotating-vector model with α and β values of 125 and -1.2^○, such that the core and conal regions can be identified with the primary and secondary polarization modes and plausibly with the extraordinary and ordinary propagation modes. The polarization modal segregation of profiles shows that the core comprises two parts, which we associate with later X-mode and earlier O-mode emission. Analysis of the broad microstructures under the core shows that they have similar time-scales to those of the largely conal radiation of other pulsars studied earlier. Aberration/retardation analysis was here possible for both the conal and core radiation and showed average physical emission heights of about 200 km for each. Comparison with other core-cone pulsars suggests that the core and conal emission arises from similar heights. Assuming the inner vacuum gap model, we note that at these emission altitudes the frequency of the observed radiation ν_obs is less than the plasma frequency ν_p. We then conclude that the radio emission properties are consistent with the theory of coherent curvature radiation by charged solitons where the condition ν_obs < ν_p is satisfied. However, the differences that exist between core and conal emission with regard to their geometric locations within a pulse, polarization and modulation properties are yet to be understood.