An all-sky survey of circular polarisation at 200 MHz
  We present results from the first all-sky radio survey in circular
polarisation. The survey uses the Murchison Widefield Array (MWA) to cover
30900 sq. deg., over declinations south of +30$^{\circ}$ and north of
-86$^{\circ}$ centred at 200 MHz (over a 169-231 MHz band). We achieve a
spatial resolution of approx. 3' and a typical sensitivity of 3.0 mJy
PSF$^{-1}$ over most of the survey region. We demonstrate a new leakage
mitigation technique that reduces the leakage from total intensity into
circular polarisation by an order of magnitude. In a blind survey of the imaged
region, we detect 14 pulsars in circular polarisation above a 6$\sigma$
threshold. We also detect six transient sources associated with artificial
satellites. A targeted survey of 2376 pulsars within the surveyed region
yielded 33 detections above $4\sigma$. Looking specifically at pulsars
previously detected at 200 MHz in total intensity, this represents a 35%
detection rate. We also conducted a targeted survey of 2400 known flare stars,
this resulted in two tentative detections above $4\sigma$. A similar targeted
search for 1506 known exoplanets in the field yielded no detections above
$4\sigma$. The success of the survey suggests that similar surveys at longer
wavelength bands and of deeper fields are warranted.
