Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

Tom E Hassall, Benjamin W Stappers, Jason W T Hessels, Michael Kramer, Anastasia Alexov, Kenneth R Anderson, Thijs Coenen, Aris Karastergiou, Evan F Keane, Vlad I Kondratiev, Kosmas Lazaridis, Joeri van Leeuwen, Aris Noutsos, Maciej Serylak, Charlotte Sobey, Joris P W Verbiest, Patrick Weltevrede, Kimon Zagkouris, Rob Fender, Ralph A M J WijersLars Bahren, Martin E Bell, Jess W Broderick, Stephane Corbel, Edward J Daw, Vik S Dhillon, Jochen Eisloffel, Heino Falcke, Jean-Mathias Griessmeier, Peter G Jonker, Casey J Law, Sera B Markoff, James C A Miller-Jones, Rachel Osten, Evert Rol, Anna M M Scaife, Bart Scheers, Pim Schellart, Hanno Spreeuw, John D Swinbank, Sander ter Veen, Michael W Wise, Rudy A D Wijnands, Olaf Wucknitz, Philippe Zarka, Ashish Asgekar, Michael R Bell, Mark J Bentum, Gianni Bernardi, Philip N Best, Annalisa Bonafede, Albert-Jan Boonstra, Michiel A Brentjens, Wim N Brouw, Marcus Bruggen, Harvey Raymond Butcher, Benedetta Ciardi, Michael A Garrett, Marchel Gerbers, Andre W Gunst, Michael P van Haarlem, George Heald, Matthias Hoeft, Hanno A Holties, Alwin de Jong, Leon V E Koopmans, Masaya Kuniyoshi, Geert Kuper, G Marcel Loose, Peter Maat, Joseph S Masters, John P McKean, Henri Meulman, Maaijke Mevius, Harm Munk, Jan E Noordam, Emanuela Orru, Harm Paas, Mamta Pandey-Pommier, Vishambar N Pandey, Roberto Pizzo, Antonis Polatidis, Wolfgang Reich, Huub J A Rottgering, Jurjen Sluman, Matthias Steinmetz, Cees G M Sterks, Michel Tagger, Yuan Tang, Cyril Tasse, Rene Vermeulen, Reinout J van Weeren, Stefan J Wijnholds, Sarod Yatawatta

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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 105 across our observing band. We use this fact to constrain some of the properties of the interstellar medium 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
Original languageEnglish
Pages (from-to)1 - 20
Number of pages20
JournalAstronomy & Astrophysics
Publication statusPublished - 2012
Externally publishedYes

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