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Session 74 - Pulsars.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[74.08] Polarimetry of Millisecond Pulsars

S. Sallmen, D. C. Backer (U. California at Berkeley), M. Kramer (MPI für Radioastronomie)

For slow pulsars, polarization studies led Radhakrishnan and Cooke to propose a (1969) rotating vector model which successfully explains the sweep of position angle seen across pulses. This polar cap model indicates that emission originates near the magnetic pole, within the region of field lines which do not close within the light cylinder, and polarimetry has been used to investigate the geometry of the emission region for these pulsars. Millisecond pulsars have much shorter spin periods (\sim ms vs. \sim s), and weaker magnetic fields (B 10^8 G vs. \sim 10^12 G) than their slower counterparts. These pulsars therefore have a very open field geometry and a much smaller light cylinder. The characteristics of their emission regions may therefore be different from those of slow pulsars, and polarimetry is probably the best diagnostic for investigating this possibility. In light of the above considerations, polarimetry data were obtained on several millisecond pulsars in 1995 January and February, using the 140' telescope at Green Bank, WV. The CDRP (Coherent Dispersion Removal Processor) developed at Berkeley was used to collect full Stokes parameters for the average profiles. Most of the data are at 800 MHz. Some data were also recorded at 1395 MHz. Calibration of the instrumental polarization effects was performed by using the well studied slow pulsar B1929+10. In addition, polarimetry data were obtained for two millisecond pulsars at the Effelsberg telescope in Germany, at 1400 MHz, using the new EBPP (Effelsberg--Berkeley--Pulsar--Processor). Polarimetry data will be presented for pulsars J1012+5307, J1022+1001, B1620-26, J1713+0747, B1821-24, and J2145-0750, and we will discuss the results.

Program listing for Wednesday