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1. Discovery of PSR J0523-7125 as a Circularly Polarized Variable Radio Source in the Large Magellanic Cloud

   https://doi.org/10.3847/1538-4357/ac61dc  

   Wang, Yuanming; Murphy, Tara; Kaplan, David L.; Klinner-Teo, Teresa; Ridolfi, Alessandro; Bailes, Matthew; Crawford, Fronefield; Dai, Shi; Dobie, Dougal; Gaensler, B. M.; et al (May 2022, The Astrophysical Journal)

   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). This RM is extreme compared to other pulsars in the LMC (more than twice that of the largest previously reported one). The average flux density of ∼1 mJy at 1400 MHz and ∼25 mJy at 400 MHz places it among the most luminous radio pulsars known. It likely evaded previous discovery because of its very steep radio spectrum (spectral index α ≈ −3, where S ν ∝ ν α ) and broad pulse profile (duty cycle ≳35%). We discuss implications for searches for unusual radio sources in continuum images, as well as extragalactic pulsars in the Magellanic Clouds and beyond. Our result highlighted the possibility of identifying pulsars, especially extreme pulsars, from radio continuum images. Future large-scale radio surveys will give us an unprecedented opportunity to discover more pulsars and potentially the most distant pulsars beyond the Magellanic Clouds. 

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2. The Extraordinary Linear Polarisation Structure of the Southern Centaurus A Lobe Revealed by ASKAP

   https://doi.org/10.3390/galaxies6040127  

   Anderson, Craig; Heald, George; O’Sullivan, Shane; Bunton, John; Carretti, Ettore; Chippendale, Aaron; Collier, Jordan; Farnes, Jamie; Gaensler, Bryan; Harvey-Smith, Lisa; et al (December 2018, Galaxies)

   We present observations of linear polarisation in the southern radio lobe of Centaurus A, conducted during commissioning of the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. We used 16 antennas to observe a 30 square degree region in a single 12-h pointing over a 240 MHz band centred on 913 MHz. Our observations achieve an angular resolution of 26 × 33 arcseconds (480 parsecs), a maximum recoverable angular scale of 30 arcminutes, and a full-band sensitivity of 85 μ Jy beam − 1 . The resulting maps of polarisation and Faraday rotation are amongst the most detailed ever made for radio lobes, with order 10 5 resolution elements covering the source. We describe several as-yet unreported observational features of the lobe, including its detailed peak Faraday depth structure, and intricate networks of depolarised filaments. These results demonstrate the exciting capabilities of ASKAP for widefield radio polarimetry. 

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3. A circular polarization survey for radio stars with the Australian SKA Pathfinder

   https://doi.org/10.1093/mnras/stab299  

   Pritchard, Joshua; Murphy, Tara; Zic, Andrew; Lynch, Christene; Heald, George; Kaplan, David L; Anderson, Craig; Banfield, Julie; Hale, Catherine; Hotan, Aidan; et al (March 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   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. These range from M-dwarfs through to magnetic, chemically peculiar A- and B-type stars. Some of these are well-known radio stars such as YZ CMi and CU Vir, but 23 have no previous radio detections. We report the flux density and derived brightness temperature of these detections and discuss the nature of the radio emission. We also discuss the implications of our results for the population statistics of radio stars in the context of future ASKAP and Square Kilometre Array surveys. 

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4. Radio AGN selection and characterization in three Deep-Drilling Fields of the Vera C. Rubin Observatory Legacy Survey of Space and Time

   https://doi.org/10.1093/mnras/stad1178  

   Zhu, Shifu; Brandt, W. N.; Zou, Fan; Luo, Bin; Ni, Qingling; Xue, Yongquan; Yan, Wei (April 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT The Australia Telescope Large Area Survey (ATLAS) and the VLA survey in the XMM-LSS/VIDEO deep field provide deep (≈15 $$\mu$$ Jy beam−1) and high-resolution (≈4.5–8 arcsec) radio coverage of the three XMM-SERVS fields (W-CDF-S, ELAIS-S1, and XMM-LSS). These data cover a total sky area of 11.3 deg2 and contain ≈11 000 radio components. Furthermore, about 3 deg2 of the XMM-LSS field also has deeper MIGHTEE data that achieve a median RMS of 5.6 $$\mu$$ Jy beam−1 and detect more than 20 000 radio sources. We analyse all these radio data and find source counterparts at other wavebands utilizing deep optical and infrared (IR) surveys. The nature of these radio sources is studied using radio-band properties (spectral slope and morphology) and the IR–radio correlation. Radio AGNs are selected and compared with those selected using other methods (e.g. X-ray). We found 1656 new AGNs that were not selected using X-ray and/or MIR methods. We constrain the FIR-to-UV SEDs of radio AGNs using cigale and investigate the dependence of radio AGN fraction upon galaxy stellar mass and star formation rate. 

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5. GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) I: Survey description and initial data release

   https://doi.org/10.1017/pasa.2022.17  

   Hurley-Walker, N.; Galvin, T. J.; Duchesne, S. W.; Zhang, X.; Morgan, J.; Hancock, P. J.; An, T.; Franzen, T. M.; Heald, G.; Ross, K.; et al (January 2022, Publications of the Astronomical Society of Australia)

   Abstract We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72–231 MHz and Declinations south of $$+30^\circ$$ have been performed with the Murchison Widefield Array “extended” Phase II configuration over 2018–2020 and will be processed to form data products including continuum and polarisation images and mosaics, multi-frequency catalogues, transient search data, and ionospheric measurements. From a pilot field described in this work, we publish an initial data release covering 1,447 $$\mathrm{deg}^2$$ over $$4\,\mathrm{h}\leq \mathrm{RA}\leq 13\,\mathrm{h}$$ , $$-32.7^\circ \leq \mathrm{Dec} \leq -20.7^\circ$$ . We process twenty frequency bands sampling 72–231 MHz, with a resolution of 2′–45 ′′ , and produce a wideband source-finding image across 170–231 MHz with a root mean square noise of $$1.27\pm0.15\,\mathrm{mJy\,beam}^{-1}$$ . Source-finding yields 78,967 components, of which 71,320 are fitted spectrally. The catalogue has a completeness of 98% at $${{\sim}}50\,\mathrm{mJy}$$ , and a reliability of 98.2% at $$5\sigma$$ rising to 99.7% at $$7\sigma$$ . A catalogue is available from Vizier; images are made available via the PASA datastore, AAO Data Central, and SkyView. This is the first in a series of data releases from the GLEAM-X survey. 

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