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C. Rodriguez, J. Rankin (University of Vermont)
Two pulsars with highly asymmetric average profiles, B0919+06 and B1859+07, were noted as exhibiting pronounced shifts in their emission window. Sensitive single-pulse polarimetric observations of these stars were conducted recently at Arecibo using both the 327-MHz and 21-cm systems. Episodes were identified in both wherein the bright emission moves to earlier longitudes in a progressing manner, remains there fore some 50 periods, and then progressively returns to its usual position near the trailing edges of the stars’ profiles. The total shift in B0919+06 is about 4 degrees, and that in B1859+07 some 10 degrees. Both the gradual change of emission phase over 10-20 periods and the fact that virtually no emission occurs at the usual phase during the shifts suggested that this might be a new type of behavior. Moreover, in B1859+07 we observed that the shifts occurred quasi-periodically at intervals of about 180 periods. Because the emission width increased in both cases during the shift, we explore whether the effect could be attributed to increases in the emission height. We also explore whether it can be regarded as a form of mode change.
One of us (CR) wishes to acknowledge a HELiX/EPSCoR Summer Research Fellowship in partial support of this work. Portions of this work were carried out with support from NSF Grant AST 99-87654. Arecibo Observatory is operated by Cornell University under contract to the US NSF.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.