In this study, the results obtained using GOES satellite X-ray data and MWO and WSO measurements of the solar magnetic field between 1976 and 2022 are compared and discussed. By analysing GOES satellite X-ray data in 47 different time periods of one month long, 7 500 solar flares are obtained, the flare equivalent duration distributions against the total duration of the flare are statistically modelled, and then their variation via time is examined. The variations of the model parameters such as the Plateau, which is considered as an indicator of the stellar saturation level in an observation season, and the flare timescales via time are examined. We noticed that the variation found in the solar magnetic field and the variation determined in the flare saturation levels are very similar. As a result, it is well known that the solar magnetic dipole moment measured from the solar poles steadily decreased from 1976 to 2022. We revealed that the solar X-ray flare energies are also generally decreasing in the same trend. This decrease is also evident in flare timescales, indicating that the geometry of solar magnetic loops is getting smaller over time.

With the low Earth orbit environment becoming increasingly populated with artificial satellites, rockets, and debris, it is important to understand the effects they have on radio astronomy. In this work, we undertake a multi-frequency, multi-epoch survey with two SKA-Low station prototypes located at the SKA-Low site, to identify and characterise radio frequency emission from orbiting objects and consider their impact on radio astronomy observations. We identified 152 unique satellites across multiple passes in low and medium Earth orbits from 1.6 million full-sky images across 13 selected ${\approx}1$ MHz frequency bands in the SKA-Low frequency range, acquired over almost 20 days of data collection. Our algorithms significantly reduce the rate of satellite misidentification, compared to previous work, validated through simulations to be $ \lt 1\%$. Notably, multiple satellites were detected transmitting unintended electromagnetic radiation, as well as several decommissioned satellites likely transmitting when the Sun illuminates their solar panels. We test alternative methods of processing data, which will be deployed for a larger, more systematic survey at SKA-Low frequencies in the near future. The current work establishes a baseline for monitoring satellite transmissions, which will be repeated in future years to assess their evolving impact on radio astronomy observations.

Galaxy Zoo is an online project to classify morphological features in extra-galactic imaging surveys with public voting. In this paper, we compare the classifications made for two different surveys, the Dark Energy Spectroscopic Instrument (DESI) imaging survey and a part of the Kilo-Degree Survey (KiDS), in the equatorial fields of the Galaxy And Mass Assembly (GAMA) survey. Our aim is to cross-validate and compare the classifications based on different imaging quality and depth. We find that generally the voting agrees globally but with substantial scatter, that is, substantial differences for individual galaxies. There is a notable higher voting fraction in favour of ‘smooth’ galaxies in the DESI+zoobot classifications, most likely due to the difference between imaging depth. DESI imaging is shallower and slightly lower resolution than KiDS and the Galaxy Zoo images do not reveal details such as disc features and thus are missed in the zoobot training sample. We check against expert visual classifications and find good agreement with KiDS-based Galaxy Zoo voting. We reproduce the results from Porter-Temple+ (2022), on the dependence of stellar mass, star formation, and specific star formation on the number of spiral arms. This shows that once corrected for redshift, the DESI Galaxy Zoo and KiDS Galaxy Zoo classifications agree well on population properties. The zoobot cross-validation increases confidence in its ability to compliment Galaxy Zoo classifications and its ability for transfer learning across surveys.

Fast radio burst (FRB) science primarily revolves around two facets: the origin of these bursts and their use in cosmological studies. This work follows from previous redshift–dispersion measure (z–DM) analyses in which we model instrumental biases and simultaneously fit population parameters and cosmological parameters to the observed population of FRBs. This sheds light on both the progenitors of FRBs and cosmological questions. Previously, we have completed similar analyses with data from the Australian Square Kilometer Array Pathfinder (ASKAP) and the Murriyang (Parkes) Multibeam system. In this manuscript, we use 119 FRBs with 29 associated redshifts by additionally modelling the Deep Synoptic Array (DSA) and the Five-hundred-metre Aperture Spherical radio Telescope (FAST). We also invoke a Markov chain Monte Carlo (MCMC) sampler and implement uncertainty in the Galactic DM contributions. The latter leads to larger uncertainties in derived model parameters than previous estimates despite the additional data and indicate that precise measurements of DM$_\textrm{ISM}$ will be important in the future. We provide refined constraints on FRB population parameters and derive a new constraint on the minimum FRB energy of log $E_{\mathrm{min}}$(erg)=39.47$^{+0.54}_{-1.28}$ which is significantly higher than bursts detected from strong repeaters. This result likely indicates a low-energy turnover in the luminosity function or may alternatively suggest that strong repeaters have a different luminosity function to single bursts. We also predict that FAST will detect 25–41% of their FRBs at $z \gtrsim 2$ and DSA will detect 2–12% of their FRBs at $z \gtrsim 1$.

The bright radio source, GLEAM J091734$-$001243 (hereafter GLEAM J0917$-$0012), was previously selected as a candidate ultra-high redshift ($z \gt 5$) radio galaxy due to its compact radio size and faint magnitude ($K(\mathrm{AB})=22.7$). Its redshift was not conclusively determined from follow-up millimetre and near-infrared spectroscopy. Here we present new HST WFC3 G141 grism observations which reveal several emission lines including [NeIII]$\lambda$3867, [NeV]$\lambda$3426 and an extended ($\approx 4.8\,$kpc), [OII]$\lambda$3727 line which confirm a redshift of $3.004\pm0.001$. The extended component of the [OII]$\lambda$3727 line is co-spatial with one of two components seen at 2.276 GHz in high resolution ($60\times 20\,$mas) Long Baseline Array data, reminiscent of the alignments seen in local compact radio galaxies. The BEAGLE stellar mass ($\approx 2\times 10^{11}\,\textit{M}_\odot$) and radio luminosity ($L_{\mathrm{500MHz}}\approx 10^{28}\,$W Hz$^{-1}$) put GLEAM J0917$-$0012 within the distribution of the brightest high-redshift radio galaxies at similar redshifts. However, it is more compact than all of them. Modelling of the radio jet demonstrates that this is a young, $\approx 50\,$kyr old, but powerful, $\approx 10^{39}\,$W, compact steep spectrum radio source. The weak constraint on the active galactic nucleus bolometric luminosity from the [NeV]$\lambda$3426 line combined with the modelled jet power tentatively implies a large black hole mass, $\ge 10^9\,\textit{M}_\odot$, and a low, advection-dominated accretion rate, i.e. an Eddington ratio $\le 0.03$. The [NeV]$\lambda$3426/[NeIII]$\lambda$3867 vs [OII]$\lambda$3727/[NeIII]$\lambda$3867 line ratios are most easily explained by radiative shock models with precursor photoionisation. Hence, we infer that the line emission is directly caused by the shocks from the jet and that this radio source is one of the youngest and most powerful known at cosmic noon. We speculate that the star-formation in GLEAM J0917$-$0012 could be on its way to becoming quenched by the jet.

Subdwarf B stars are a well-known class of hot, low-mass stars thought to be formed through interactions in stellar binary systems. While different formation channels for subdwarf B stars have been studied through a binary population synthesis approach, it has also become evident that the characteristics of the found populations depend on the initial set of assumptions that describe the sometimes poorly constrained physical processes, such as common envelope episodes or angular momentum loss during mass transfer events. In this work we present a parameter study of subdwarf B populations, including a novel analytic prescription that approximates the evolution of subdwarf B stars with hydrogen-rich outer shells, an element previously overlooked in rapid binary population synthesis. We find that all studied parameters strongly impact the properties of the population, with the possibility of igniting helium below the expected core-mass value near the tip of the red giant branch strongly affecting the total number of subdwarf B candidates. Critically, our newly proposed prescription for the evolution of subdwarf B stars with hydrogen-shells helps to reconcile theoretical predictions of surface gravity and effective temperature with observational results. Our prescription is useful in the context of rapid binary population synthesis studies and can be applied to other rapid binary population synthesis codes’ output.