Traditional pulsar surveys have primarily employed time-domain periodicity searches. However, these methods are susceptible to effects like scattering, eclipses, and orbital motion. At lower radio frequencies ($\lesssim$300 MHz), factors such as dispersion measure and pulse broadening become more prominent, reducing the detection sensitivity. On the other hand, image domain searches for pulsars are not limited by these effects and can extend the parameter space to regions inaccessible to traditional search techniques. Therefore, we have developed a pipeline to form 1-second full Stokes images from offline correlated high time-resolution data from the Murchison Widefield Array (MWA). This led to the development of image-based methodologies to identify new pulsar candidates. In this paper, we applied these methodologies to perform a low-frequency image-based pulsar census of the galactic plane (12 MWA observations, covering $\sim$6 000 $\textrm{deg}^\textrm{2}$ sky). This work focuses on the detection of the known pulsar population which were present in the observed region of the sky using both image-based and beamformed methods. This resulted in the detection of 83 known pulsars, with 16 pulsars found only in Stokes I images but not in periodicity searches applied in beamformed data. Notably, for 14 pulsars these are the first reported low-frequency detections. This underscores the importance of image-based searches for pulsars that may be undetectable in time-series data, due to scattering and/or dispersive smearing at low frequencies. This highlights the importance of low-frequency flux density measurements in refining pulsar spectral models and investigating the spectral turnover of pulsars at low frequencies.

Fast Radio Bursts (FRBs) are millisecond dispersed radio pulses of predominately extra-galactic origin. Although originally discovered at GHz frequencies, most FRBs have been detected between 400 and 800 MHz. Nevertheless, only a handful of FRBs were detected at radio frequencies $\le$400 MHz. Searching for FRBs at low frequencies is computationally challenging due to increased dispersive delay that must be accounted for. Nevertheless, the wide field of view (FoV) of low-frequency telescopes – such as the the Murchison Widefield Array (MWA), and prototype stations of the low-frequency Square Kilometre Array (SKA-Low) – makes them promising instruments to open a low-frequency window on FRB event rates, and constrain FRB emission models. The standard approach, inherited from high-frequencies, is to form multiple tied-array beams to tessellate the entire FoV and perform the search on the resulting time series. This approach, however, may not be optimal for low-frequency interferometers due to their large FoVs and high spatial resolutions leading to a large number of beams. Consequently, there are regions of parameter space in terms of number of antennas and resolution elements (pixels) where interferometric imaging is computationally more efficient. Here we present a new high-time resolution imager BLINK implemented on modern graphical processing units (GPUs) and intended for radio astronomy data. The main goal for this imager is to become part of a fully GPU-accelerated FRB search pipeline. We describe the imager and present its verification on real and simulated data processed to form all-sky and widefield images from the MWA and prototype SKA-Low stations. We also present and compare benchmarks of the GPU and CPU code executed on laptops, desktop computers, and Australian supercomputers. The code is publicly available at https://github.com/PaCER-BLINK-Project/imager and can be applied to data from any radio telescope.

In order to study exoplanets, a comprehensive characterisation of the fundamental properties of the host stars – such as angular diameter, temperature, luminosity, and age, is essential, as the formation and evolution of exoplanets are directly influenced by the host stars at various points in time. In this paper, we present interferometric observations taken of directly imaged planet host 51 Eridani at the CHARA Array. We measure the limb-darkened angular diameter of 51 Eridani to be $\theta_\mathrm{LD} = 0.450\pm 0.006$ mas and combining with the Gaia zero-point corrected parallax, we get a stellar radius of $1.45 \pm 0.02$ R$_{\odot}$. We use the PARSEC isochrones to estimate an age of $23.2^{+1.7}_{-2.0}$ Myr and a mass of $1.550^{+0.006}_{-0.005}$ M$_{\odot}$. The age and mass agree well with values in the literature, determined through a variety of methods ranging from dynamical age trace-backs to lithium depletion boundary methods. We derive a mass of $4.1\pm0.4$ M$_\mathrm{Jup}$ for 51 Eri b using the Sonora Bobcat models, which further supports the possibility of 51 Eri b forming under either the hot-start formation model or the warm-start formation model.

In gamma-ray binaries neutron star is orbiting a companion that produces a strong stellar wind. We demonstrate that observed properties of ‘stellar wind’–‘pulsar wind’ interaction depend both on the overall wind thrust ratio, as well as more subtle geometrical factors: the relative direction of the pulsar’s spin, the plane of the orbit, the direction of motion, and the instantaneous line of sight. Using fully 3D relativistic magnetohydrodynamical simulations we find that the resulting intrinsic morphologies can be significantly orbital phase-dependent: a given system may change from tailward-open to tailward-closed shapes. As a result, the region of unshocked pulsar wind can change by an order of magnitude over a quarter of the orbit. We calculate radiation maps and synthetic light curves for synchrotron (X-ray) and inverse-Compton emission (GeV-TeV), taking into account $\gamma $–$\gamma $ absorption. Our modelled light curves are in agreement with the phase-dependent observed light curves of LS5039.

The interaction between stellar winds and the partially ionized local interstellar medium (LISM) is quite common in astrophysics. However, the main difficulty in describing the neutral components lies in the fact that the mean free path of an interstellar atom, l, can be comparable to the characteristic size of an astrosphere, L (i.e. the Knudsen number, which is equal to l/L, is approximately equal to 1, as in the case of the heliosphere). In such cases, a single-fluid approximation becomes invalid, and a kinetic description must be used for the neutral component. In this study, we consider a general astrosphere and use a kinetic-gas dynamics model to investigate how the global structure of the astrosphere depends on the Knudsen number. We present numerical results covering an extremely wide range of Knudsen numbers (from 0.0001 to 100). Additionally, we explore the applicability of single-fluid approaches for modelling astrospheres of various sizes. We have excluded the influence of interstellar and stellar magnetic fields in our model to make parametric study of the kinetic effects feasible. The main conclusion of this work is that, for large astrospheres (with a distance to the bow shock greater than 600 AU) a heated rarefied plasma layer forms in the outer shock layer near the astropause. The formation of this layer is linked to localized heating of the plasma by atoms (specifically, ENAs) that undergo charge exchange again behind the astropause. This process significantly alters the flow structure in the outer shock layer and the location of the bow shock, and it cannot be described by a single-fluid model. Additionally, this paper discusses how atoms weaken the bow shocks at near-heliospheric conditions.