Establishing the Fundamental Physics and Interactions of Coherent Radio and Thermal X-ray Emission from Pulsars

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Pulsars are rapidly spinning, highly magnetized, and very compact stars, which were discovered just over fifty years ago. The light from pulsars is usually detected as radio waves or X rays. The radio waves are emitted from charged plasma flowing along the pulsar's magnetic field lines, while the X rays are emitted from very hot (hence "thermal") surface areas, heated by backflowing plasma. While the broad picture of pulsar radio and X-ray emission is known, many of the details are yet to be fully understood. A research team at the University of Vermont will carry out a three part observational and theoretical program aimed at providing insight into pulsar emission mechanisms and studying the Milky Way's interstellar magnetic field. The radio observations have been or will be conducted primarily with the Very Large Array, Arecibo, LOFAR and Green Bank. X-ray observations have been made using the XMM-Newton satellite. The first part of the program involves confirmation and extension of pulsar radio emission physics. The second part will connect thermal X-ray to radio emission. The third part will use pulsar measurements to help to understand the magnetic field in the plane of our Galaxy. Undergraduate research students will be extensively involved in the projects and will receive invaluable scientific training that is simply not available in the classroom.Through observational interpretation and computer modeling of the pulsar magnetosphere, astronomers now understand how charge currents are generated and where they flow, outlining the broad mechanisms of pulsar radio emission: where it is generated and how part of it escapes. The planned study will advance capabilities to relate the emission physics to global magnetospheric processes, and provide the needed specificity for theorists to develop physical models for charged soliton radiation. The research team will also use simultaneous X-ray and radio observations of pulsars with multiple emission states in order to learn how the backflow heating associated with thermal X-ray emission is connected to changes in the radio emission properties, and will identify candidate pulsars for future joint X-ray/radio investigations. The nature, structure, and origin of the Galactic magnetic field is only partially understood. The project will include analyses of extensive, existing pulsar Faraday rotation measurements of distant and faint pulsars to contribute significantly to the understanding of the magnetic field in the plane of our Galaxy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.