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1 Jodrell Bank Centre for Astrophysics 2 ASTRON - ASTRON 3 MPIFR - Max-Planck-Institut für Radioastronomie 4 Astrophysics, University of Oxford 5 USN - Unité Scientifique de la Station de Nançay 6 LPC2E - Laboratoire de Physique et Chimie de l-Environnement et de l-Espace 7 University of Southampton Southampton, UK 8 AI PANNEKOEK - Astronomical Institute Anton Pannekoek 9 AIM - UMR 7158 - UMR E 9005 - Astrophysique Interactions Multi-échelles 10 The University of Sheffield Sheffield 11 Thüringer Landessternwarte Tautenburg 12 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics 13 STSci - Space Telescope Science Institute 14 School of Physics and Astronomy Southampton 15 Argelander Institut für Astronomie 16 LESIA - Laboratoire d-études spatiales et d-instrumentation en astrophysique 17 Max Planck Institute for Astrophysics 18 CfA - Harvard-Smithsonian Center for Astrophysics 19 University of Edinburgh 20 Jacobs University Bremen 21 KAPTEYN ASTRONOMICAL INSTITUTE - Kapteyn Astronomical Institute 22 LEIDEN OBSERVATORY - Leiden Observatory 23 NRAO - NRAO 24 IMAPP - Applied Stochastics 25 CRAL - Centre de Recherche Astrophysique de Lyon 26 Leibniz Institute DSMZ Germany 27 Center for Information Technology CIT 28 Rhodes University 29 SKA South Africa

Abstract : Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR at 40-190 MHz, the 76-m Lovell Telescope at 1400 MHz and the Effelsberg 100-m Telescope at 8000 MHz to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 100000 across our observing band. We use this fact to constrain some of the properties of the ISM along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays.

Keywords : magnetic fields telescopes pulsars: general ISM: general

Autor: T. E. Hassall - B. W. Stappers - J. W. T. Hessels - M. Kramer - A. Alexov - K. Anderson - T. Coenen - A. Karastergiou - E. F. Kea

Fuente: https://hal.archives-ouvertes.fr/


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