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Pulse profile modelling (PPM) is a comprehensive relativistic ray-tracing technique employed to determine the properties of neutron stars. In this study, we apply this technique to the Type I X-ray burster and accretion-powered millisecond pulsar XTE J1814−338, extracting its fundamental properties using PPM of its thermonuclear burst oscillations. Using data from its 2003 outburst, and a single uniform temperature hotspot model, we infer XTE J1814−338 to be located at a distance of |$7.2^{+0.3}_{-0.4}$| kpc, with a mass of |$1.21^{+0.05}_{-0.05}$| M |$_\odot$| and an equatorial radius of |$7.0^{+0.4}_{-0.4}$| km. Our results also offer insight into the time evolution of the hotspot but point to some potential shortcomings of the single uniform temperature hotspot model. We explore the implications of this result, including what we can learn about thermonuclear burst oscillation mechanisms and the importance of modelling the accretion contribution to the emission during the burst. [ABSTRACT FROM AUTHOR]

Spider pulsars are millisecond pulsars in short-period (≲12-h) orbits with low-mass (~0.01–0.4 M⊙) companion stars. The pulsars ablate plasma from the companion star, causing time delays and eclipses of the radio emission from the pulsar. The magnetic field of the companion has been proposed to strongly influence both the evolution of the binary system1 and the eclipse properties of the pulsar emission2. Changes in the rotation measure (RM) have been seen in a spider system, implying that there is an increase in the magnetic field near the eclipse3. Here we report a diverse range of evidence for a highly magnetized environment in the spider system PSR B1744 – 24A4, located in the globular cluster Terzan 5. We observe semi-regular profile changes to the circular polarization, V, when the pulsar emission passes close to the companion. This suggests that there is Faraday conversion where the radio wave tracks a reversal in the parallel magnetic field and constrains the companion magnetic field, B (> 10 G). We also see irregular, fast changes in the RM at random orbital phases, implying that the magnetic strength of the stellar wind, B, is greater than 10 mG. There are similarities between the unusual polarization behaviour of PSR B1744 – 24A and some repeating fast radio bursts (FRBs)5–7. Together with the possible binary-produced long-term periodicity of two active repeating FRBs8,9, and the discovery of a nearby FRB in a globular cluster10, where pulsar binaries are common, these similarities suggest that a proportion of FRBs have binary companions.The observation of pulsar emission at various orbital phases of a companion star probes the diverse magnetic structure in a binary system, and exhibits varying polarization behavior, akin to that observed in certain fast radio bursts. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) must be powered by uniquely energetic emission mechanisms. This requirement has eliminated a number of possible source types, but several remain. Identifying the physical nature of FRB emitters arguably requires good localisation of more detections, as well as broad-band studies enabled by real-time alerting. In this paper, we present the Apertif Radio Transient System (ARTS), a supercomputing radio-telescope instrument that performs real-time FRB detection and localisation on the Westerbork Synthesis Radio Telescope (WSRT) interferometer. It reaches coherent-addition sensitivity over the entire field of the view of the primary-dish beam. After commissioning results verified that the system performed as planned, we initiated the Apertif FRB survey (ALERT). Over the first 5 weeks we observed at design sensitivity in 2019, we detected five new FRBs, and interferometrically localised each of them to 0.4-10 sq. arcmin. All detections are broad band, very narrow, of the order of 1 ms in duration, and unscattered. Dispersion measures are generally high. Only through the very high time and frequency resolution of ARTS are these hard-to-find FRBs detected, producing an unbiased view of the intrinsic population properties. Most localisation regions are small enough to rule out the presence of associated persistent radio sources. Three FRBs cut through the halos of M31 and M33. We demonstrate that Apertif can localise one-off FRBs with an accuracy that maps magneto-ionic material along well-defined lines of sight. The rate of one every days ensures a considerable number of new sources are detected for such a study. The combination of the detection rate and localisation accuracy exemplified by the first five ARTS FRBs thus marks a new phase in which a growing number of bursts can be used to probe our Universe. [ABSTRACT FROM AUTHOR]

PSR B0943+10 is an old non-recycled pulsar which for decades has been mostly known for its rapid and spontaneous radio mode switching. Recently, Hermsen et al. (2013) discovered correlated changes in the thermal X-ray emission from the polar cap, thus demonstrating that radio modes are not just a product of the local changes in the radio emission region, but a sign of some global magnetospheric transformation. At about the same time, owing to the commissioning of the new generation of low-frequency radio arrays, the broadband observations at the lowest edge of ionospheric transparency window became available. At these radio frequencies profile morphology and the single-pulse properties of PSR B0943+10's emission become very dynamic, providing details not only about the emission itself, but also about the conditions in the polar gap. Here, I will present the recent results of the LOFAR observations of PSR B0943+10 and discuss their contribution to the multiwavelength picture. [ABSTRACT FROM AUTHOR]

We have used sensitive LOw Frequency ARray (LOFAR) observations of PSR B0809+74 at 15–62 MHz to study the anomalously intensive pulses, first reported by Ulyanov et al. (2006) at 18–30 MHz. Similarly to Ulyanov et al. , we found that the spectra of strong pulses consist of distinct bright patches. Moreover, these spectral patches were spotted to drift upwards in frequency over the course of several pulse sequences. We established that this drift is not pulsar-intrinsic, but is caused by the broadband ~20 second-long enhancements of recorded signal, which influenced the dispersed tracks of several pulses at once. We speculate on the cause of such enhancements (i.e. propagation or telescope-related) and the ramifications they bring to the single-pulse studies at the very low radio frequencies. Depending on the origin, the phenomenon may also affect the analysis of highly dispersed single pulses at higher radio frequencies, e.g. Fast Radio Bursts. [ABSTRACT FROM AUTHOR]

Both the physics of the pulsar emission mechanism and free-free absorption in the intervening interstellar medium can be tested with the pulsar radio spectra. We have built on our previous work on describing LOFAR population of millisecond pulsars (MSPs; Kondratiev et al. 2016) and HBA census of slow pulsars (Bilous et al. 2016) and present the study of radio spectra of the MSPs with a special attention on the low-frequency turnover. Using LOFAR timing data allowed us to measure flux densities of many MSPs over time span of up to three years in the frequency range 110–188 MHz. This provided more reliable estimates of mean flux densities and spectra reducing the influence of refractive scintillation, ionosphere and other factors on a single flux measurement. Together with published data at other radio frequencies we constructed pulsars' spectra and fitted them with single or broken power-laws. We discuss the obtained spectra and their fits, paying special attention to the low-frequency turnover, and compare broadband radio spectra of MSPs to those of normal pulsars. [ABSTRACT FROM AUTHOR]