Pulsar polarimetry at mm-wavelengths

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Session 48 -- Degenerate Stars and Pulsars
Display presentation, Thursday, June 15, 1995, 9:20am - 4:00pm

[48.05] Pulsar polarimetry at mm-wavelengths

K. M. Xilouris, M. Kramer (Arecibo Observatory, Max-Planck Institut for Radioastronomy)

Following the detection of eight pulsars at mm-wavelengths, we have conducted polarimetric observations at 32 GHz aimed at probing the emission properties of this newly-explored region of the pulsar spectrum.

The measured flux densities between 27.9 and 34.8 GHz suggest that the spectra of some pulsars in our sample flatten towards higher frequencies, or even exhibit turn-ups. The multiplicity of pulse-profiles which often characterizes the emission at UHF and microwave frequencies, is replaced by simple Gaussian forms at mm-wavelengths in most of the cases studied. The high degree of linear polarization found at lower frequencies has significantly dropped by the mm-wavelength region, and in most cases the emission appears completely depolarized. However, PSR B0355+54 maintains a high degree of linear polarization, allowing the polarization position angle to be measured as a function of pulse longitude. This curve, although defined over a much-narrower range of pulsar longitude, maintains the same slope with frequency as at lower frequencies, suggesting that the underlying magnetic field configuration has not deviated significantly from that relevant to the site of lower-frequency emission. The dominance of a dipole field configuration, even at the extremely-low magnetospheric altitudes at which the mm-wave emission is currently thought to originate, is further supported by the measured profile-width narrowing. For the pulsars in our sample this narrowing ceases or significantly slows down for frequencies higher than the middle of the microwave band ($\sim 5 GHz$).

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