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A. Kirchner (Carleton College), N.D.R. Bhat (NAIC)
Inspired by recent pulsar observations with the upgraded Arecibo telescope of wisp-like interstellar scintillation phenomenon, we analyzed pulsar scintillation data taken with the Ooty Radio Telescope at 327 MHz (Bhat et al. 1999). We have been able to make unambiguous detections of "wisp-like" features for several pulsars, with their nature varying from pulsar to pulsar.
Wisps are faint, diffuse features extending outward from the origin of secondary spectra of pulsar scintillation. Secondary interstellar scintillation spectra (i.e., distribution of points in plane of inverse frequency and inverse time) are derived by taking the 2-dimensional Fourier transform of dynamic spectra ( i.e., pulse intensity in time and frequency).
With the multi-epoch nature of our data, we have investigated several aspects of wisp features, in particular their time variability and statistics of occurrence. Our analysis shows wisps are prominent for nearby (within approximately 1 kpc) pulsars. Our analysis also suggests an interesting correspondence between the nature of wisps, specifically their left/right dominance, and the general elongation of diffractive scintillation patterns in the pulsar dynamic spectrum.
Funding was provided by the National Science Foundation. Research was done as part of the NSF REU program at Arecibo Observatory (NAIC).