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 Vela's X-ray emission and radio arrival times on a pulse-by-pulse basis. At a confidence level of 99.8% we have 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 second X-ray peak during radio pulses that arrive later. Our results suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption of radio emission in the outer magnetosphere as a cause of the X-ray emission are explored as a possible explanation for the correlation.
Lommen, A., Donovan, J., Gwinn, C., Arzoumanian, Z., Harding, A., Strickman, M., Dodson, R., Mcculloch, P., & Moffett, D. (2007). Correlation between X-ray light-curve shape and radio arrival time in the Vela pulsar. The Astrophysical Journal, 657(1), 436-440. https://doi.org/10.1086/510797