Pulsars identified in the LOFAR Two-metre Sky Survey at 144 MHz

¹ Leiden Observatory, Leiden University, PO Box 9500, 2300 RA Leiden, The Netherlands
² ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 29 September 2025
Accepted: 8 December 2025

Abstract

We present the astrometric identification of 80 known radio pulsars as unresolved continuum sources detected at 144 MHz in the second data release of the LOFAR Two-metre Sky Survey (LoTSS DR2), which covers 27% of the northern hemisphere. These identifications represent the majority (≥86%) of radio pulsars present in the LoTSS DR2 footprint and provide independent celestial positions and flux densities at 144 MHz. We compare LoTSS flux densities with literature values from various image- and time-domain observations and find good agreement for all but two pulsars. We attribute these flux density deviations to intrinsic pulsar properties (nulling and off-pulse emission). We investigate criteria to select promising pulsar candidates using data from the upcoming LoTSS release of the entire northern sky (δ > 0°), as well as the LOFAR LBA Sky Survey (LoLSS) at 54 MHz (covering δ > 24°). Of the 80 detections, 35 (44%) were blindly redetected based on their linear or circular polarization. Therefore, we conclude that candidate selection based on polarization properties is a promising approach. Candidate selection can be supplemented with spectral indices via cross-matching to LoLSS sources at 54 MHz, as the high sensitivity of LoTSS is not matched by image-domain surveys at higher frequencies.