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M. L. Boyer (University of Minnesota), Y. Gupta (NAIC, Arecibo and NCRA, Pune)
Observations taken simultaneously over three frequencies (240, 325, & 610 MHz) with the GMRT in India, of the pulsar PSR B3029+54 reveal a general trend for the core component of high intensity pulses to arrive earlier than for less intense pulses. Statistical analyses of the data also show a trend that this phase shift of the core decreases at the higher frequencies. Similar analysis of simultaneous data taken over a larger frequency range (240, 610, 1410, & 4850 MHz, using the GMRT in combination with the Jodrell Bank and Effelsberg telescopes) confirms this trend, with the shift almost vanishing at the highest frequency. Analyses of PSR B1642-03 (simultaneous at 240 & 610 MHz) and of PSR B2111+46 (at 320MHz) also show similar intensity dependent phase shifts. Thus, this may be a generic effect for the core component emission of pulsars. Our analysis when applied to the strong, conal pulsar PSR B1133+16 (at 240, 610, 1410, & 4850 MHz) show no apparent trend of phase shift across frequency or intensity for the conal components. We argue that these findings support the hypothesis that, for core components, more intense pulses originate at higher altitudes in the pulsar magnetosphere than less intense pulses. The range of variation is found to be 140 to 2100 kilometers.
This research was funded by an REU grant from the National Science Foundation through Cornell University. Research took place at Arecibo Observatory, operated by Cornell University under contract to the National Science Foundation.
The author(s) of this abstract have provided an email address for comments about the abstract: boye0010@umn.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.