The Commensal Real-time Australian Square Kilometre Array Pathfinder Fast Transients survey is the first extensive astronomical survey using phased array feeds. Since January 2017, it has been searching for fast radio bursts in fly’s eye mode. Here, we present a calculation of the sensitivity and total exposure of the survey that detected the first 20 of these bursts, using the pulsars B1641-45 and B0833-45 as calibrators. The beamshape, antenna-dependent system noise, and the effects of radio-frequency interference and fluctuations during commissioning are quantified. Effective survey exposures and sensitivities are calculated as a function of the source counts distribution. Statistical ‘stat’ and systematics ‘sys’ effects are treated separately. The implied fast radio burst rate is significantly lower than the 37 sky−1 day−1 calculated using nominal exposures and sensitivities for this same sample by Shannon et al. (2018). At the Euclidean (best-fit) power-law index of −1.5 (−2.2), the rate is $12.7_{-2.2}^{+3.3}$ (sys) ± 3.6 (stat) sky−1 day−1 ( $20.7_{-1.7}^{+2.1}$ (sys) ± 2.8 (stat) sky−1 day−1) above a threshold of 56.6 ± 6.6(sys) Jy ms (40.4 ± 1.2(sys) Jy ms). This strongly suggests that these calculations be performed for other FRB-hunting experiments, allowing meaningful comparisons to be made between them.

This paper describes the technical details and practical implementation of the phase synchronisation system selected for use by the Mid-Frequency Square Kilometre Array. Over a four-year period, the system has been tested on metropolitan fibre-optic networks, on long-haul overhead fibre at the South African Square Kilometre Array site, and on existing telescopes in Australia to verify its functional performance. The tests have shown that the system exceeds the 1-s Square Kilometre Array coherence loss requirement by a factor of 2 560, the 60-s coherence loss requirement by a factor of 239, and the 10-min phase drift requirement by almost five orders-of-magnitude. The paper also reports on tests showing that the system can operate within specification over all the required operating conditions, including maximum fibre link distance, temperature range, temperature gradient, relative humidity, wind speed, seismic resilience, electromagnetic compliance, frequency offset, and other operational requirements.

This paper uses population synthesis to investigate the possible origin of isolated millisecond pulsars as born from the coalescence of a neutron star and a white dwarf. Results show that the galactic birth rate of isolated millisecond pulsars is likely to lie between 5.8×10−5 yr−1 and 2.0×10−4 yr−1, depending on critical variables, such as the stability of mass transfer via the Roche lobe and the value of kick velocity. In addition to this, this paper estimates that the solar mass of isolated millisecond pulsars can range from 1.5 and 2.0 Mʘ, making them more massive than other ‘normal’ pulsars. Finally, the majority of isolated millisecond pulsars in our simulations have spin periods ranging from several to 20 ms, which is consistent with previous observations.

Stars of 8–10 M⊙ form a strongly electron-degenerate oxygen–neon–magnesium core which is more massive than ∼1.1 M⊙, and become super-Asymptotic Giant Branch stars. The oxygen–neon–magnesium core increases its mass through H and He shell burning. The core contracts accordingly and the central density increases. In the high density core, electron capture takes place and further boosts the core contraction. When electron capture on 20Ne starts, it induces oxygen–neon deflagration. It remains a theoretical question whether neutron star can be formed after the deflagration has started. If the star collapses, the following explosion is known as an electron capture supernova. In this article, we give a brief overview on the development of idea in the presupernova evolution and the hydrodynamics behaviour of electron capture supernovae. Using standard stellar evolutionary models that show rather high ignition density, we show that the collapse can occur in a wide range of model parameter. However, future study remains important. We also review the possible observables of electron capture supernovae and discuss their applications to the light curve model for the Crab supernova 1054.

The GaLactic and Extragalactic All-sky Murchison Widefield Array survey is a radio continuum survey at 72–231 MHz of the whole sky south of declination +30º, carried out with the Murchison Widefield Array. In this paper, we derive source counts from the GaLactic and Extragalactic All-sky Murchison data at 200, 154, 118, and 88 MHz, to a flux density limit of 50, 80, 120, and 290 mJy respectively, correcting for ionospheric smearing, incompleteness and source blending. These counts are more accurate than other counts in the literature at similar frequencies as a result of the large area of sky covered and this survey’s sensitivity to extended emission missed by other surveys. At S154 MHz > 0.5 Jy, there is no evidence of flattening in the average spectral index (α ≈ −0.8 where S ∝ vα) towards the lower frequencies. We demonstrate that the Square Kilometre Array Design Study model by Wilman et al. significantly underpredicts the observed 154-MHz GaLactic and Extragalactic All-sky Murchison counts, particularly at the bright end. Using deeper Low-Frequency Array counts and the Square Kilometre Array Design Study model, we find that sidelobe confusion dominates the thermal noise and classical confusion at v ≳ 100 MHz due to both the limited CLEANing depth and the undeconvolved sources outside the field-of-view. We show that we can approach the theoretical noise limit using a more efficient and automated CLEAN algorithm.

We describe the parameters of a low-frequency all-sky survey of compact radio sources using Interplanetary Scintillation, undertaken with the Murchison Widefield Array. While this survey gives important complementary information to low-resolution survey, providing information on the sub-arsecond structure of every source, a survey of this kind has not been attempted in the era of low-frequency imaging arrays such as the Murchison Widefield Array and LOw Frequency Array. Here we set out the capabilities of such a survey, describing the limitations imposed by the heliocentric observing geometry and by the instrument itself. We demonstrate the potential for Interplanetary Scintillation measurements at any point on the celestial sphere and we show that at 160 MHz, reasonable results can be obtained within 30° of the ecliptic (2π str: half the sky). We also suggest some observational strategies and describe the first such survey, the Murchison Widefield Array Phase I Interplanetary Scintillation survey. Finally we analyse the potential of the recently upgraded Murchison Widefield Array and discuss the potential of the Square Kilometre Array-low to use Interplanetary Scintillation to probe sub-mJy flux density levels at sub-arcsecond angular resolution.

Indications from Gaia data release 2 are that the tip of the red giant branch (a population II standard candle related to the helium flash in low mass stars) is close to –4 in absolute I magnitude in the Cousins photometric system. Our sample is high-latitude southern stars from the thick disk and inner halo, and our result is consistent with longstanding findings from globular clusters, whose distances were calibrated with RR Lyrae stars. As the Gaia mission proceeds, there is every reason to think an accurate Galactic geometric calibration of tip of the red giant branch will be a significant outcome for the extragalactic distance scale.