New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR

D Carbone¹, A J van der Horst², R A M J Wijers¹, J D Swinbank³, A Rowlinson⁴, J W Broderick⁵, Y N Cendes¹, A J Stewart⁶, M E Bell⁷, R P Breton⁸, S Corbel⁹, J Eislöffel¹⁰, R P Fender⁶, J-M Grießmeier¹¹, J W T Hessels¹², P Jonker¹³, M Kramer¹⁴, C J Law¹⁵, J C A Miller-Jones¹⁶, M Pietka⁶, L H A Scheers¹⁷, B W Stappers⁸, J van Leeuwen¹², R Wijnands¹, M Wise¹², P Zarka¹⁸

Affiliations

¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands.
² Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Department of Physics, The George Washington University, 725 21 Street NW, Washington, DC 20052, USA.
³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA.
⁴ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia; ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands.
⁵ ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands; Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK; Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
⁶ Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK.
⁷ CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia; ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), The University of Sydney, NSW 2006, Australia.
⁸ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK.
⁹ Laboratoire AIM (CEA/IRFU - CNRS/INSU - Université Paris Diderot), CEA DSM/IRFU/SAp, F-91191 Gif-sur-Yvette, France; Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, USR 704 - Univ. Orléans, OSUC, F-18330 Nançay, France.
¹⁰ Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany.
¹¹ Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, USR 704 - Univ. Orléans, OSUC, F-18330 Nançay, France; Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, LPC2E UMR 7328 CNRS, F-45071 Orléans, France.
¹² Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands.
¹³ SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584-CA Utrecht, the Netherlands; Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands.
¹⁴ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK; Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
¹⁵ Department of Astronomy and Radio Astronomy Lab, University of California, Berkeley, CA, USA.
¹⁶ International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
¹⁷ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Centrum Wiskunde & Informatica, PO Box 94079, NL-1090 GB Amsterdam, the Netherlands.
¹⁸ LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, F-92195 Meudon, France.

PMID: 27279785
DOI: 10.1093/mnras/stw539

New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR

D Carbone et al. Mon Not R Astron Soc. 2016.

. 2016 Mar 7;459(3):3161-3174.

doi: 10.1093/mnras/stw539. eCollection 2016 Jul 1.

Authors

Affiliations

¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands.
² Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Department of Physics, The George Washington University, 725 21 Street NW, Washington, DC 20052, USA.
³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA.
⁴ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia; ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands.
⁵ ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands; Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK; Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK.
⁶ Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK.
⁷ CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia; ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), The University of Sydney, NSW 2006, Australia.
⁸ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK.
⁹ Laboratoire AIM (CEA/IRFU - CNRS/INSU - Université Paris Diderot), CEA DSM/IRFU/SAp, F-91191 Gif-sur-Yvette, France; Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, USR 704 - Univ. Orléans, OSUC, F-18330 Nançay, France.
¹⁰ Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany.
¹¹ Station de Radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, USR 704 - Univ. Orléans, OSUC, F-18330 Nançay, France; Laboratoire de Physique et Chimie de l'Environnement et de l'Espace, LPC2E UMR 7328 CNRS, F-45071 Orléans, France.
¹² Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands.
¹³ SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584-CA Utrecht, the Netherlands; Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands.
¹⁴ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK; Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany.
¹⁵ Department of Astronomy and Radio Astronomy Lab, University of California, Berkeley, CA, USA.
¹⁶ International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
¹⁷ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands; Centrum Wiskunde & Informatica, PO Box 94079, NL-1090 GB Amsterdam, the Netherlands.
¹⁸ LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, F-92195 Meudon, France.

PMID: 27279785
DOI: 10.1093/mnras/stw539

Abstract

We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg². We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10^-3 deg^-2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.

Keywords: instrumentation: interferometers; methods: data analysis; methods: statistical; radio continuum: general; techniques: image processing.

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New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR

Affiliations

New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR

Authors

Affiliations

Abstract

LinkOut - more resources

Full Text Sources

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