Previous | Session 111 | Next
J. H. Crossley, T. H. Hankins, J. A. Eilek (New Mexico Tech)
The occasional anomalous scattering of the Crab Nebula pulsar radio pulses has been attributed to the passage of emission-line filaments in the outer regions of the Crab nebula through the line of sight to the star. We have made 100-ns-resolution observations of giant pulses from the Crab pulsar and analyzed the height, width and arrival time of microstructure within each giant pulse. We report here on echoes we found in our 1.4-GHz observations on 1996 October 14. The echo emission was consistently present during 2.8 hours of main pulse observations but was not detected in observations performed 2 days before or after. Echo emission was not seen in simultaneous 4.9-GHz observations of the same pulses.
The echo component at 1.4 GHz is delayed by 45 microseconds, has 10 percent the maximum flux and has roughly twice the width of its corresponding primary. Based on the short time span of this echo event and the absence of echo emission in giant pulses at 4.9 GHz, it is improbable that the observed phenomenon is associated with the nebular filaments. Instead we suggest these echoes are due to scattering by the smaller "wisps" located at the interface between the pulsar wind and the synchrotron nebula.
We also present giant pulse echoes we observed during a 1997 November scattering event that has been associated with the nebular filaments by other authors, and we discuss differences between the two data sets.
The author(s) of this abstract have provided an email address for comments about the abstract: jcrossle@nrao.edu
Previous | Session 111 | Next
Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.