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Astron. Astrophys. 324, 981-987 (1997)

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Does radius-to-frequency mapping persist
close to the pulsar surface?

A. von Hoensbroech 1 and K.M.  Xilouris 2

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
2 Cornell University, National Astronomy & Ionospheric Center, Arecibo Observatory, P.O. Box 995, Arecibo, PR 00613, USA

Received 14 October 1996 / Accepted 24 February 1997

Abstract

A major uncertainty in our understanding of pulsar emission physics is the location of the radio emission region in pulsar magnetospheres. The narrowing of the intensity profile width with increasing frequency has traditionally been taken as observational evidence supporting a radius-to-frequency mapping in pulsar magnetospheres. Here, 64 high-quality polarimetric profiles at cm-wavelengths have been analyzed to probe for the first time the emission radius at presumably deeper layers of pulsar magnetospheres. Interpreting polarization measurements in the context of the modified relativistic rotating-vector model (Blaskiewicz et al. 1991), we derive emission altitudes and compare our results with the geometrical predictions of a rotating dipolar configuration. We conclude that for slow pulsars the emission is consistent with heights ranging between 1 and 2 [FORMULA] of the light-cylinder radius. Only a slight radius-to-frequency mapping is evident at cm-wavelengths which saturates progressively with frequency. The consistency between the results of the two methods further supports the persistence of an undisturbed dipole field throughout the magnetospheres of slow pulsars.

Key words: pulsars: general – pulsars: PSR B0136+57, PSR B0301+19, PSR B0329+54, PSR B0355+54, PSR B0450+55, PSR B0525+21, PSR B0540+23, PSR B0740 – 28, PSR B0809+74, PSR B0823+26, PSR B0919+06, PSR B0950+08, PSR B1133+16, PSR B1237+35, PSR B1642 – 03, PSR B1822 – 09, PSR B1915+13, PSR B1929+10, PSR B1946+35, PSR B2016+28, PSR B2020+28, PSR B2154+40, PSR B2021+51, PSR B2045 – 16, PSR B2310+42, PSR B2319+60, PSR B2351+61 – polarization

Send offprint requests to: A. von  Hoensbroech (avh@mpifr-bonn.mpg.de)

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© European Southern Observatory (ESO) 1997

Online publication: May 5, 1998

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