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The ASKAP Variables and Slow Transients Survey (VAST)
is designed to detect highly variable and transient radio sources on timescales from 5 seconds
to ∼5 years.
Murphy et al. have recently presented initial results
from the VAST Phase I Pilot Survey.
An initial search revealed 28 highly variable and/or transient sources.
One class of variable sources was pulsars, as illustrated in
yesterday's ADAP.
For this pulsar,
variability is most likely due to refractive interstellar scintillation on longer timescales
and diffractive interstellar scintillation on shorter timescales.
The left panel above shows the VAST Stokes I (total intensity) image for the
epoch with the maximum flux density. The middle panel shows the Stokes V (circular polarisation)
image for the same epoch where positive flux density
corresponds to right handed circular polarisation and negative to left handed.
The ellipse in the lower left corner of each radio image
shows the FWHM of the restoring beam. The right panels show
Stokes I contours at 30, 60, and 90 per cent of the peak Stokes I flux
density overlaid on an RGB image of optical data from the Dark Energy Survey with red=i-band,
green=r-band, blue=g-band.
This pulsar shows negligible circular polarisation, and like most pulsars,
is not detectable at optical wavelengths.
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