Correlations between pulsed X-ray flux and radio arrival time in the Vela pulsar

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray and radio flux densities and radio arrival times on a pulse by pulse basis. We found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. We suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption in the outer magnetosphere as a cause of the radio emission, and less directly of the X-ray emission, are explored as a possible explanation for the correlation.