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Abstract We report the discovery of a highly circularly polarized, variable, steep-spectrum pulsar in the Australian Square Kilometre Array Pathfinder (ASKAP) Variables and Slow Transients (VAST) survey. The pulsar is located about 1° from the center of the Large Magellanic Cloud, and has a significant fractional circular polarization of ∼20%. We discovered pulsations with a period of 322.5 ms, dispersion measure (DM) of 157.5 pc cm −3 , and rotation measure (RM) of +456 rad m −2 using observations from the MeerKAT and the Parkes telescopes. This DM firmly places the source, PSR J0523−7125, in the Large Magellanic Cloud (LMC).more »Free, publicly-accessible full text available May 1, 2023
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Free, publicly-accessible full text available October 1, 2022
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ABSTRACT We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-h observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-min model-subtracted images with sensitivity of $\sim\! 200\, \mu$Jy/beam; two of them are extreme intra-hour variables with modulation indices up to $\sim 40{{\ \rm per\ cent}}$ and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼1 arcminmore »
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ABSTRACT We present a search for radio afterglows from long gamma-ray bursts using the Australian Square Kilometre Array Pathfinder (ASKAP). Our search used the Rapid ASKAP Continuum Survey, covering the entire celestial sphere south of declination +41○, and three epochs of the Variables and Slow Transients Pilot Survey (Phase 1), covering ∼5000 square degrees per epoch. The observations we used from these surveys spanned a nine-month period from 2019 April 21 to 2020 January 11. We cross-matched radio sources found in these surveys with 779 well-localized (to ≤15 arcsec) long gamma-ray bursts occurring after 2004 and determined whether the associationsmore »
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ABSTRACT We present results from a circular polarization survey for radio stars in the Rapid ASKAP Continuum Survey (RACS). RACS is a survey of the entire sky south of δ = +41○ being conducted with the Australian Square Kilometre Array Pathfinder telescope (ASKAP) over a 288 MHz wide band centred on 887.5 MHz. The data we analyse include Stokes I and V polarization products to an RMS sensitivity of 250 μJy PSF−1. We searched RACS for sources with fractional circular polarization above 6 per cent, and after excluding imaging artefacts, polarization leakage, and known pulsars we identified radio emission coincident with 33 known stars.more »
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Abstract We have found a class of circular radio objects in the Evolutionary Map of the Universe Pilot Survey, using the Australian Square Kilometre Array Pathfinder telescope. The objects appear in radio images as circular edge-brightened discs, about one arcmin diameter, that are unlike other objects previously reported in the literature. We explore several possible mechanisms that might cause these objects, but none seems to be a compelling explanation.
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ABSTRACT Active M dwarfs are known to produce bursty radio emission, and multiwavelength studies have shown that solar-like magnetic activity occurs in these stars. However, coherent bursts from active M dwarfs have often been difficult to interpret in the solar activity paradigm. We present Australian Square Array Pathfinder (ASKAP) observations of UV Ceti at a central frequency of 888 MHz. We detect several periodic, coherent pulses occurring over a time-scale consistent with the rotational period of UV Ceti. The properties of the pulsed emission show that they originate from the electron cyclotron maser instability, in a cavity at least 7 orders of magnitudemore »