The UTR-2 decametre pulsar and transient survey

I. Transient detection

¹ Institute of Radio Astronomy of NAS of Ukraine, 4 Mystetstv st., 61002 Kharkiv, Ukraine
² V. N. Karazin Kharkiv National University, 4 Svobody Sq., 61022 Kharkiv, Ukraine
³ LPC2E, OSUC, Univ Orléans, CNRS, CNES, Observatoire de Paris, 45071 Orléans, France
⁴ Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, USA
⁵ Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA, USA
⁶ LIRA, Observatoire de Paris, CNRS, PSL, Sorbonne U., U. Paris Cité, Meudon, France
⁷ ORN, Observatoire de Paris, CNRS, PSL, U. Orléans, Nançay, France

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

Received: 3 April 2025
Accepted: 11 February 2026

Abstract

Context. This paper presents a detailed description of the Decametre Pulsar and Transient Survey of the Northern Sky that was carried out in 2012–2017 using the world’s largest radio telescope at decametre wavelengths – UTR-2 in Ukraine. This extensive survey covers the northern sky from declination −10^◦ to +80^◦, with a temporal resolution of 8 ms, and explores dispersion measures up to 30 pc/cm³.

Aims. The major advantage of the decametre wavelength range is a comparatively wide band (∆f / f ∼ 1), in which the dispersive delay due to the interstellar plasma reaches hundreds of seconds, giving us the opportunity to determine the dispersion measure with a very high accuracy. This enables us to discover new transients, while avoiding data contamination from numerous weak signals of a different nature.

Methods. The drift-scan survey in 5-beam mode of UTR-2 was carried out at night time. To cover the entire sky along the right ascension, the duration of the sessions was more than 12 hours at a time close to the autumn and spring equinoxes (to obtain the same conditions for the interference situation). 90 degrees along the declination were covered by five beams in ∼40 days (each equinox).

Results. We discovered 380 individual transient signals with dispersion measures significantly differ from those of known sources. We determined the parameters of each single transient signal. We show that they cannot be explained by ionospheric scintillations. Repeated observations have shown that some detected transient signals are repetitive and are thus likely to originate from pulsars or rotating radio transients.