Observations and modelling of pulsed radio emission from CU Virginis

TL;DR

This study observes pulsed radio emissions from CU Virginis at multiple wavelengths, confirming previous detections and proposing a magnetospheric model involving plasma refraction to explain the frequency-dependent pulse timing.

Contribution

It provides new multi-frequency radio observations and develops a magnetospheric model that explains the observed pulse timing behavior through plasma refraction effects.

Findings

Detection of two circularly polarized pulses per rotation confirming previous results.

The pulse timing order reverses between frequencies, explained by plasma refraction.

Electron cyclotron maser emission model is inconsistent with data.

Abstract

We present 13 cm and 20 cm radio observations of the magnetic chemically peculiar star CU Virginis taken with the Australia Telescope Compact Array. We detect two circularly polarised radio pulses every rotation period which confirm previous detections. In the first pulse, the lower frequency emission arrives before the higher frequency emission and the ordering reverses in the second pulse. In order to explain the frequency dependence of the time between the two pulses, we construct a geometric model of the magnetosphere of CU Virginis, and consider various emission angles relative to the magnetic field lines. A simple electron cyclotron maser emission model, in which the emission is perpendicular to the magnetic field lines, is not consistent with our data. A model in which the emission is refracted through cold plasma in the magnetosphere is shown to have the correct pulse arrival time frequency dependence.