I. P. Kravtsov | Searcharxiv

arXiv2026

The UTR-2 decametre pulsar and transient survey I. Transient detection

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 deg , with a temporal resolution of 8 ms, and explores dispersion measures up to 30 pc/cc. Aims. The major advantage of the decametre wavelength range is a comparatively wide band, 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. Key words. Stars: neutron - pulsars: general - Methods: data analysis - Methods: observational - Astronomical databases: Surveys

astro-ph.GA↗

arXiv2023

Constraining the magnetic field geometry of the millisecond pulsar PSR~J0030+0451 from joint radio, thermal X-ray and $γ$-ray emission

With the advent of multi-wavelength electromagnetic observations of neutron stars, spanning many decades in photon energies, from radio wavelengths up to X-rays and $γ$-rays, it becomes possible to significantly constrain the geometry and the location of the associated emission regions. In this work, we use results from the modelling of thermal X-ray observations of PSR~J0030+0451 from the NICER mission and phase-aligned radio and $γ$-ray pulse profiles to constrain the geometry of an off-centred dipole able to reproduce the light-curves in these respective bands simultaneously. To this aim, we deduce a configuration with a simple dipole off-centred from the location of the centre of the thermal X-ray hot spots and show that the geometry is compatible with independent constraints from radio and $γ$-ray pulsations only, leading to a fixed magnetic obliquity of $α\approx 75°$ and a line of sight inclination angle of $ζ\approx 54°$. We demonstrate that an off-centred dipole cannot be rejected by accounting for the thermal X-ray pulse profiles. Moreover, the crescent shape of one spot is interpreted as the consequence of a small scale surface dipole on top of the large scale off-centred dipole.

astro-ph.HE↗