Pulsar scintillation studies with LOFAR

III. Annual variations in PSR J0814+7429

¹ State Key Laboratory of Radio Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
² University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100049, China
³ Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China
⁴ Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
⁵ CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
⁶ Guizhou Radio Astronomical Observatory, Guizhou University, Guiyang 550001, China
⁷ National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411007, Maharashtra, India
⁸ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁹ Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str 1, 85741 Garching, Germany
¹⁰ Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Astronomisches Institut, 44780 Bochum, Germany
¹¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
¹² Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8, Canada
¹³ Trottier Space Institute, McGill University, 3550 rue University, Montréal, QC H3A 2A7, Canada
¹⁴ Dipartimento di Fisica “G. Occhialini”, Università di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
¹⁵ INFN, Sezione di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
¹⁶ INAF - Osservatorio Astronomico di Cagliari, via della Scienza 5, 09047 Selargius (CA), Italy
¹⁷ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
¹⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
¹⁹ National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China

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Received: 24 October 2025
Accepted: 1 April 2026

Abstract

Context. The interstellar scintillation observed in radio pulsars arises from interference between electromagnetic waves scattered by electron density fluctuations in the turbulent interstellar plasma, providing a critical tool for probing the small-scale structure of the ionized interstellar medium and the pulsar system itself.

Aims. The primary aim of this work is to study long-term scintillation variations for a bright and nearby pulsar, PSR J0814+7429, carried out from September 2013 to September 2023 with the LOw-Frequency ARray (LOFAR) High Band Antennae in the frequency range 120-170 MHz.

Methods. We derived the basic scintillation parameters, scintillation bandwidth (Δν_d), and scintillation timescale (Δτ_d) from the twodimensional (2D) auto-covariance function of the dynamic spectra that are a 2D matrix of pulse intensity as a function of time and frequency.

Results. We present a long-term monitoring study of Δν_d and Δτ_d for PSR J0814+7429, which shows a strong annual variation in the time series of the Δτ_d. From our modeling of the annual variations of scintillation velocities, the scattering screen is anisotropic and located at 0.23 ± 0.02 kpc from the Earth, likely corresponding to the boundary of the Local Bubble.