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Pritchard et al. present results from a circular polarisation survey for radio stars
in the
Rapid ASKAP Continuum Survey (RACS).
Circular polarisation surveys are a promising method for widefield
detection of radio stars, as the synchrotron emission from background
Active Galactic Nuclei (AGN) is typically less than 2 per cent
circularly-polarised, and thus the number of false-positive matches
between stars and unrelated AGN is significantly reduced.
The team searched RACS for sources with fractional circular polarisation
above 6 per cent and, after excluding imaging artefacts, polarisation
leakage, and known pulsars, they identified radio emission coincident
with 33 known stars, 23 of which had no previous radio detections.
These range from M-dwarfs through to magnetic,
chemically peculiar A- and B-type stars.
The images above are of the cool dwarf star CD−44 1173.
Cool dwarfs typically
produce non-thermal radio emission in magnetically confined
coronae.
CD−44 1173 is a young K-type in the Tucana-Horologium
moving group with rotationally modulated optical variability
that has previously exhibited ultraviolet flares and X-ray activity.
The RACS detection is the first radio detection of the star.
RACS data is shown in Stokes I (total intensity, left panel) and Stokes V
(circular polarisation, middle panel).
The ellipse in the lower left corner of each radio image shows
the restoring beam. The right panel shows the RACS Stokes I contours overlaid
on optical data from the ANU
Skymapper telescope.
More details are given in
the paper
published in Monthly Notices of the Royal Astronomical Society.
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