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Rotation measure variations for 20 millisecond pulsars |
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| Authors: | W M Yan R N Manchester G Hobbs W van Straten J E Reynolds N Wang M Bailes N D R Bhat S Burke-Spolaor D J Champion A Chaudhary W A Coles A W Hotan J Khoo S Oslowski J M Sarkissian D R B Yardley |
| Institution: | 1. Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science-1 Street, Urumqi, Xinjiang, 830011, China 2. Graduate University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China 3. CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, NSW, 1710, Australia 4. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC, 3122, Australia 5. Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing, 210008, China 6. Max-Planck-Institut f??r Radioastronomie, Auf dem H??gel 69, 53121, Bonn, Germany 7. Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA, USA 8. Sydney Institute for Astronomy, School of Physics, The University of Sydney, Sydney, NSW, 2006, Australia |
| Abstract: | We report on variations in the mean position angle of the 20 millisecond pulsars being observed as part of the Parkes Pulsar Timing Array (PPTA) project. It is found that the observed variations are dominated by changes in the Faraday rotation occurring in the Earth??s ionosphere. Two ionospheric models are used to correct for the ionospheric contribution and it is found that one based on the International Reference Ionosphere gave the best results. Little or no significant long-term variation in interstellar RM was found with limits typically about 0.1 rad?m?2?yr?1 in absolute value. In a few cases, apparently significant RM variations over timescales of a few 100 days or more were seen. These are unlikely to be due to localised magnetised regions crossing the line of sight since the implied magnetic fields are too high. Most probably they are statistical fluctuations due to random spatial and temporal variations in the interstellar electron density and magnetic field along the line of sight. |
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