The LOFAR pilot surveys for pulsars and fast radio transients^⋆

¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
e-mail: leeuwen@astron.nl
² ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
³ Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
⁴ Astro Space Center of the Lebedev Physical Institute, Profsoyuznaya str. 84/32, 117997 Moscow, Russia
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁶ School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
⁷ Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁸ National Centre for Radio Astrophysics, Post Bag 3, Ganeshkhind, 411 007 Pune, India
⁹ Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, LPC2E UMR 7328 CNRS, 45071 Orléans, France
¹⁰ Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, 18330 Nançay, France
¹¹ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹² Centre for Astrophysics and Supercomputing,Swinburne University of Technology, Mail H30, PO Box 218, VIC 3122, Australia
¹³ ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)  
¹⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
¹⁵ Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
¹⁶ SURFsara, PO Box 94613, 1090 GP Amsterdam, The Netherlands
¹⁷ Helmholtz-Zentrum Potsdam, DeutschesGeoForschungsZentrum GFZ, Department 1: Geodesy and Remote Sensing, Telegrafenberg, A17, 14473 Potsdam, Germany
¹⁸ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹⁹ Shell Technology Center, Bangalore, India
²⁰ SRON Netherlands Insitute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
²¹ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
²² CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia
²³ University of Twente, The Netherlands
²⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
²⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
²⁶ University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
²⁷ Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Obs., via Cotter Road, Weston, A.C.T. 2611, Australia
²⁸ Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, 85741 Garching, Germany
²⁹ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
³⁰ Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
³¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
³² SmarterVision BV, Oostersingel 5, 9401 JX Assen, The Netherlands
³³ Astronomisches Institut der Ruhr-Universität Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany
³⁴ Radio Astronomy Lab, UC Berkeley, CA, USA
³⁵ Sodankylä Geophysical Observatory, University of Oulu, Tähteläntie 62, 99600 Sodankylä, Finland
³⁶ STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK
³⁷ Center for Information Technology (CIT), University of Groningen, The Netherlands
³⁸ Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon, 9 Av. Charles André, 69561 Saint Genis Laval Cedex, France
³⁹ Department of Physics and Elelctronics, Rhodes University, PO Box 94, 6140 Grahamstown, South Africa
⁴⁰ SKA South Africa, 3rd Floor, The Park, Park Road, 7405 Pinelands, South Africa
⁴¹ LESIA, UMR CNRS 8109, Observatoire de Paris, 92195 Meudon, France

Received: 28 June 2014
Accepted: 1 August 2014

Abstract

We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the first low-frequency fast-radio burst limit and the discovery of two new pulsars. The first survey, the LOFAR Pilot Pulsar Survey (LPPS), observed a large fraction of the northern sky, ~ 1.4 × 10⁴ deg², with 1 h dwell times. Each observation covered ~75 deg² using 7 independent fields formed by incoherently summing the high-band antenna fields. The second pilot survey, the LOFAR Tied-Array Survey (LOTAS), spanned ~600 deg², with roughly a 5-fold increase in sensitivity compared with LPPS. Using a coherent sum of the 6 LOFAR “Superterp” stations, we formed 19 tied-array beams, together covering 4 deg² per pointing. From LPPS we derive a limit on the occurrence, at 142 MHz, of dispersed radio bursts of < 150 day^-1 sky^-1, for bursts brighter than S> 107 Jy for the narrowest searched burst duration of 0.66 ms. In LPPS, we re-detected 65 previously known pulsars. LOTAS discovered two pulsars, the first with LOFAR or any digital aperture array. LOTAS also re-detected 27 previously known pulsars. These pilot studies show that LOFAR can efficiently carry out all-sky surveys for pulsars and fast transients, and they set the stage for further surveying efforts using LOFAR and the planned low-frequency component of the Square Kilometer Array.