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J. E. Espinoza Goodman, K. M. Becker (Oberlin), J. M. Cordes (Cornell), M. A. Kramer (Oberlin), M. A. McLaughlin (Cornell), J. L. Sheckard (CfA), T. C. T. Smith, D. R. Stinebring (Oberlin)
We have made high-resolution, high-sensitivity dynamic spectra of a sample of strong pulsars at 430~MHz with the Arecibo radiotelescope. For 4 pulsars we find faint but sharply delineated parabolic arcs in the secondary spectra. These features correspond to the ``crisscross'' or ``multiple drift slope'' phenomenon previously observerd in pulsar dynamic spectra. The unprecedented resolution and dynamic range of the data allow new insights into the the properties of the scattering material and scattered image. We find that multiple imaging of the pulsar by the ISM is required. We explore thin screen scattering models and report on the agreement between our data and a compact central image surrounded by a faint scattering halo. Distances to the scattering screen along the line of sight are also calculated and found to agree well with those inferred from other scintillation phenomena.
We acknowledge support from the National Science Foundation: grants AST-9618408, AST-9619493, and NSF 9819931.