Pulsars with NenuFAR: Backend and pipelines

¹ LPC2E – Université d’Orléans/CNRS, France
e-mail: louis.bondonneau@obspm.fr
² Station de Radioastronomie de Nançay, Observatoire de Paris – CNRS/INSU, USR 704 – Univ. Orléans, OSUC, Route de Souesmes, 18330 Nançay, France
³ Laboratoire Univers et Théories LUTh, Observatoire de Paris, CNRS/INSU, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
⁴ ASTRON, the Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo 7991 PD, The Netherlands
⁵ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁶ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
⁷ INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, Italy
⁸ Universitá di Cagliari, Dipartimento di Fisica, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato, Italy
⁹ South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory 7925, South Africa
¹⁰ Department of Physics and Astronomy, University of the Western Cape, Bellville, Cape Town 7535, South Africa
¹¹ Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
¹² Department of Radio Astronomy Equipment and Methods of Observations, Institute of Radio Astronomy of NAS of Ukraine, Kharkiv, Ukraine
¹³ Department of Astronomy and Space Computer Science, V. N. Karazin Kharkiv National University, Kharkiv, Ukraine
¹⁴ LESIA, Observatoire de Paris, CNRS, PSL, SU/UP/UO, 92195 Meudon, France
¹⁵ AIM, CEA, CNRS, Université de Paris, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
¹⁶ SUBATECH, Institut Mines-Telecom Atlantique, CNRS/IN2P3, Université de Nantes, 44307 Nantes, France
¹⁷ GEPI Observatoire de Paris, CNRS, PSL, SU/UP/UO, 92195 Meudon, France
¹⁸ Center for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa

Received: 4 September 2020
Accepted: 1 March 2021

Abstract

Context. NenuFAR (New extension in Nançay upgrading LOFAR) is a new radio telescope developed and built on the site of the Nançay Radio Observatory. It is designed to observe the largely unexplored frequency window from 10 to 85 MHz, offering a high sensitivity across its full bandwidth. NenuFAR has started its “early science” operation in July 2019, with 58% of its final collecting area.

Aims. Pulsars are one of the major phenomena utilized in the scientific exploitation of this frequency range and represent an important challenge in terms of instrumentation. Designing instrumentation at these frequencies is complicated by the need to compensate for the effects of both the interstellar medium and the ionosphere on the observed signal. We have designed a dedicated backend and developed a complete pulsar observation and data analysis pipeline, which we describe in detail in the present paper, together with first science results illustrating the diversity of the pulsar observing modes.

Methods. Our real-time pipeline LUPPI (Low frequency Ultimate Pulsar Processing Instrumentation) is able to cope with a high data rate and provide real-time coherent de-dispersion down to the lowest frequencies reached by NenuFAR (10 MHz). The full backend functionality is described, as the available pulsar observing modes (folded, single-pulse, waveform, and dynamic spectrum).

Results. We also present some of the early science results of NenuFAR on pulsars: the detection of 12 millisecond pulsars (eight of which are detected for the first time below 100 MHz); a high-frequency resolution mapping of the PSR B1919+21 emission profile and a detailed observation of single-pulse substructures from PSR B0809+74 down to 16 MHz; the high rate of giant-pulse emission from the Crab pulsar detected at 68.7 MHz (43 events per minute); and the illustration of the very good timing performance of the instrumentation, which allows us to study dispersion measure variations in great detail.