Detecting cosmic rays with the LOFAR radio telescope

¹ Department of Astrophysics/IMAPPRadboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
e-mail: P.Schellart@astro.ru.nl
² Nikhef, Science Park Amsterdam, 1098 XG Amsterdam, The Netherlands
³ Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ KVI, University Groningen, 9747 AA Groningen, The Netherlands
⁶ ECAP, University of Erlangen-Nuremberg, 91058 Erlangen, Germany
⁷ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
⁸ Kapteyn AstronomicalInstitute, PO Box 800, 9700 AV Groningen, The Netherlands
⁹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁰ Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
¹¹ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹² School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
¹³ Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, 85741 Garching, Germany
¹⁴ International Centre for Radio Astronomy Research – Curtin University, GPO Box U1987, WA 6845 Perth, Australia
¹⁵ STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK
¹⁶ Institute for Astronomy, University of Edinburgh, Royal Observatory of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁷ LESIA, UMR CNRS 8109, Observatoire de Paris, 92195 Meudon, France
¹⁸ Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹⁹ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
²⁰ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
²¹ Astronomisches Institut der Ruhr-Universität Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany
²² Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, LPC2E UMR 7328 CNRS, 45071 Orléans Cedex 02, France
²³ SRON Netherlands Insitute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
²⁴ Center for Information Technology (CIT), University of Groningen, The Netherlands
²⁵ Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon, 9 av Charles André, 69561 Saint Genis Laval Cedex, France
²⁶ ARC Centre of Excellence for All-sky astrophysics (CAASTRO), Sydney Institute of Astronomy, University of Sydney, Australia
²⁷ University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
²⁸ Astro Space Center of the Lebedev Physical Institute, Profsoyuznaya str. 84/32, 117997 Moscow, Russia
²⁹ Centre for Radio Astronomy Techniques & Technologies (RATT), Department of Physics and Electronics, Rhodes University, PO Box 94, 6140 Grahamstown, South Africa
³⁰ SKA South Africa, 3rd Floor, The Park, Park Road, 7405 Pinelands, South Africa
³¹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
³² Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
³³ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³⁴ Sodankylä Geophysical Observatory, University of Oulu, Tähteläntie 62, 99600 Sodankylä, Finland
³⁵ Netherlands eScience Center, Science Park 140, 1098 XG Amsterdam, The Netherlands
³⁶ Fakultät fur Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany

Received: 16 September 2013
Accepted: 4 November 2013

Abstract

The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first ~2 years of observing, 405 cosmic-ray events in the energy range of 10¹⁶−10¹⁸ eV have been detected in the band from 30−80 MHz. Each of these air showers is registered with up to ~1000 independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.